It's a Monday morning in Weston-super-Mare and a year 8 class at Worle Community school are doing a drama lesson. In charge is Nancy Powell-Brace, 55, who has been working here for 22 years.

It's the second time I've met her. She reminds me of the teachers who always got the best out of me and my friends when life was all double geography and regular tedium: she has an innate sense of fun and an instinctive bond with her students, but also makes it plain – via the odd well-timed "Shhh!", chiefly – that there have to be limits. The week before I visit her, she was a contestant on Come Dine With Me (she came second, with food and entertainment inspired by The Sound Of Music).

This morning's class of 27 13-year-olds has an hour of drama once a fortnight. Today, they're tackling a morality tale about bullying called The Terrible Fate Of Humpty Dumpty. Watching what happens is a reminder of the magic a good teacher can work. The highlight is an exercise in which seven of the class take on the role of bullies accused of having something to do with Humpty's death – and are sent outside to improvise a fake alibi. Three are then cross-examined by their peers, and it's a hoot; but it's also about teamwork, performance, public speaking and more, and Powell-Brace manages to both critique and encourage them.

Unfortunately, this academic year will be her last. Now that the government has raised teachers' retirement age, she could carry on for at least 10 years, but she wants out. Drama is being sidelined, she says, and teaching is falling into a cold fog of targets, endless new "strategies" and the idea that someone's education is reducible to a set of results.

Fifteen years ago, Powell-Brace would put on annual productions, with a cast of over 100 and the help of 30 other staff: The Wizard Of Oz, Guys And Dolls, The Boyfriend. "Big productions," she says. "The school was renowned for its drama."

Now students in year 11 (fifth form, in old money) can't devote time to such activities in case it disrupts exam preparation; funding has dried up; and the hall is endlessly used for the exams taken in the run-up to GCSEs. In any case, the government sees drama as a "soft" subject, best pushed to the margins of the curriculum.

"I saw something on TV last night, about the rise in stress in 16- to 24-year-olds," she says, "and I think being so driven by results is part of it. We have strategies at school that encourage the kids to want to do better. And of course you want them to do better. But they shouldn't feel that, if they don't, they've failed." The same exacting logic, she says, applies to teachers, too: "You feel you're being judged all the time, not trusted to get on with the job you've been trained to do."

Time was, 60 kids would be studying GCSE drama at any one time. Now, it's half that. Yet drama, she says, can instill fundamental life skills. "It teaches people how to cooperate, to listen, to put aside their differences and compromise." The increasingly mechanistic model of education in England may "turn out people well qualified on paper for a job, but they won't be able to hold down the job, because they won't know how to deal with people and the world they've been thrown into."

So, come July, she'll be off. "Teaching's been my life." She wells up. "I've loved it and got so much from it. But I don't want to be here any more."

‘There’s an atmosphere of oppression,' says drama teacher Nancy Powell-Brace. 'People feel they’re being held to ransom.’ Photograph: Jon Tonks for the Guardian

If you have kids and they're at state schools, you may be at least vaguely aware of the morale crisis gripping the profession. The primary teacher you meet each morning might seem harried and in need of a break; the secondary school staff you see at parents' evenings may be worn out. A recent survey by the Department for Education (DfE) found that, on average, teachers reported working over 50 hours a week – primary staff just shy of 60. A majority of teachers said they spent some or most of their time on "unnecessary or bureaucratic" tasks, and 45% said this aspect of their work had increased. Both 2012 and 2013 saw regional strikes by the two biggest teaching unions, over pay, pensions and workload, and the National Union of Teachers has called a national strike on 26 March.

In January 2013, more than half of the teachers who responded to a YouGov survey for the NUT said their morale was low or very low, and 77% agreed the government was having a negative impact on education. And last December, the other big teaching union, the NASUWT, revealed that over half its 230,000 membership had considered quitting their jobs in the previous 12 months. Even the government's own figures say that 40% of new teachers quit within their first five years. And there is a palpable sense of fear hanging over the profession: contrary to the myth that far too many of them are gobby militants, it takes me a month's worth of calls to find teachers who will talk to me on the record; the remainder are happy to explain their predicament, but insist on being anonymous.

As a lot of teachers see it, they are the focus of bitter hostility from ministers and educational high-ups, and the victims of an increasingly oppressive machine. Schools are swamping their pupils and staff in data and targets, leaving no room for the kind of human values that were once at the centre of what teachers did. These aspects of education, teachers say, also distort their priorities, so filling in spreadsheets sometimes takes precedence over actually teaching kids.

History teacher, 28, east London: "If I don't take work home in the evening, I feel guilty, and if I don't work at weekends, I worry that I haven't done anything for two days. In the holidays, there's a lot of marking and planning, and revision sessions. I'm 28 and don't have any children or extra responsibilities, but I'm worried about the future: this is my career, it's what I want to do, but how will I do it with a family?"

For over 20 years there has been angry argument about how much formal testing goes on in English schools, and the tyranny of official rankings. After around three years at primary school, children are the subject of mandatory "teacher assessments", and at 11 they sit watershed tests known as Sats. Whether schools are seen as successful is partly down to their place in the league tables that rank their results: GCSEs and A-levels in secondary schools and sixth-form colleges; Sats in primaries.

Much of the way state education now works is traceable to the last government, and a succession of Labour education secretaries who left teachers punch-drunk. But Michael Gove, secretary of state for education since 2010, is in a different league, and is using the machinery bequeathed to him to drive through a real revolution and defeat an educational "establishment" he calls "the blob".

Like most politicians, Gove paints his plans in primary colours, but close up, what he's doing is so mind-bogglingly complicated that many teachers – let alone parents – have difficulty keeping up. The national curriculum has been rewritten, to ensure that five-year-olds can do fractions, nine-year-olds know about relative clauses and 11-year-olds are taught poetry by rote. Gove is set on doing away with levels (the grades children are currently given) and has made noises about the drawbacks of incessant testing. But he has also enthused about "regular, demanding, rigorous examinations" and in certain cases there are actually plans for more tests: new compulsory assessments for four- and five-year-olds are coming, and last month Gove suggested all state-educated 13-year-olds should sit the Common Entrance exams used by private schools. Meanwhile, there is speculation that children will effectively be given a pass or fail at the end of each school year – and, among teachers, a fatalistic belief that, whatever its drawbacks, the current mountain of targets and tests will remain because schools have got so used to it.

There are plans for drastic changes to GCSEs: starting with English language, English literature and maths, coursework will be done away with, results will be decided by a single summer exam, and grades will be numbers rather than letters. Gove is pushing for more schools to become academies, which can employ unqualified staff (as can the government's 174 new "free schools"). And his next big move is the introduction, from September, of performance-related pay, a change that has only increased teachers' dismay.

Newly-qualified primary schoolteacher, east London: "I work in quite a deprived area, and our data's in the danger zone, so there's lots of pressure. I do getting on for 60 hours a week. On new teacher's pay, that's around minimum wage. Four people I trained with have already left teaching. Once this year's out of the way, I plan to set up music tutoring and switch to supply work: if I continue on this road it'll kill my love of teaching."

There is another significant player in this story: Ofsted (the Office for Standards in Education, Children's Services and Skills), which has been in existence for 21 years. It is Ofsted that decides whether a school is "outstanding", "good", "requires improvement" or is "inadequate", and whose inspectors pay close attention to the data that teachers now spend endless hours compiling.

The state of Ofsted's relations with Gove became headline news when he sacked its chair, Baroness Morgan. But up until recently Ofsted and its chief inspector, Michael Wilshaw, one-time head of the renowned Mossbourne Academy in Hackney, have tended to be in step with the government. Before he began the job in January 2012, Wilshaw looked back on his time as a head and said: "If anyone says to you that staff morale is at an all-time low, you will know you are doing something right." In May 2012, he added: "Teachers do not know what stress is." His pronouncements are music to the ears of large swaths of the press who paint teachers as lazy, leftwing reprobates, who habitually go on strike and snooze their way through long summer holidays (which Gove, inevitably, wants rid of).

Talk to teachers about their work and Ofsted comes up within minutes. Inspectors visit schools at least once every three years and pass judgment on everything they do. Teachers are assessed on the basis of short observations and often prepare for inspections with an almost neurotic devotion (staying up all night is not uncommon). Woe betide any school given an overall 4, which denotes "inadequate" and can easily mean the arrival of "special measures" – which, if a school is still run by a local authority, usually means swift conversion into an academy, with all the disruption that entails. Passage into this dread category can be swift and unexpected, and though Ofsted denies it, there are widespread claims that inspections are being manipulated so as to ensure more schools become academies.

"There's an atmosphere of oppression," Powell-Brace says. "People think Ofsted is punitive rather than supportive. At my school, people believe they're being held to ransom." Ofsted inspectors last paid Worle Community a visit two years ago, identified "areas for development" and said they would soon be back to see how things were going. They have yet to show up. "So every week for the past 18 months, every member of staff has gone into school on edge, thinking, 'Is it going to be this week?' It's a huge thing, Ofsted coming in. You can't imagine the pressure it puts on people."

English teacher Sarah Cumberlidge: ‘Children don’t achieve in straight lines. Puberty happens. Some, especially the brighter ones, are struggling.’ Photograph: Christopher Thomond for the Guardian

Sarah Cumberlidge is 30 and teaches at a secondary school an hour's commute from her home in Sheffield, which means getting up for work at 5.30 every morning. When she did her A-levels, her English literature teacher would occasionally get the class to teach each other, and he thought she stood out: "He was like, 'You're a natural. You should be a teacher.'" After graduating in English, she spent two years working for H&M, but realised she was "getting nowhere" and studied for a postgraduate certificate in education, or PGCE.

She has had her current job for six years. "I'm passionate about literature, and getting to share that with kids is brilliant. I've taught Of Mice And Men, like, 25 million times, but every time the kids come out with new stuff I've never thought of. That's wonderful." There is a sadness in what she says, related to government plans to make the study of English literature at GCSE optional, and she says finding the space thoroughly to teach her students about plays, poetry and novels can be a struggle. "The hardest thing," she says, "is that I never feel what I'm doing is good enough. No matter how hard I work, my to-do list is never cleared. You can never be outstanding all the time. They just give us impossible targets."

And who are "they"? "Ofsted, I suppose." Her school had its last inspection just before Christmas 2013. "Everyone was like, 'Shit!' Everyone freaks out; everyone's terrified. So much was resting on it: we knew if we got 'requires improvement', it would be hideous. We were scared for our jobs."

English and special needs teacher, 42, central London; founder of teacherroar.blogspot.com: "People feel their professionalism's been taken away because it's all about getting kids to pass tests. Passing a test is not necessarily learning: it's a snapshot of one day. We're not equipping kids with critical thinking. With years 10 and 11, we're just endlessly redoing exam papers. I became an English teacher because I love literature and want to inspire kids. But we're just drilling them."

What she has to do day-to-day, she says, is reducible to the so-called "flight paths" that map students' projected progress through school. "They're straight lines that say what they should be achieving. But children don't achieve in a straight line. Puberty happens, and all sorts. But there's constant pressure. We put in data for each child every term, and if they are not on target, we have to justify why. You're not allowed to say, 'This kid's naughty' or, 'This kid doesn't listen.' You've got to say all the things you put in place to make sure that child is achieving. And that's constant."

What does this regime do to the kids? "It's heartbreaking, sometimes. You get kids to do a controlled assessment in English: they do a really good piece in exam conditions, and you know it's a true reflection of their ability. They've worked hard on it and they're proud of it. But because it doesn't represent four levels' progress, they have to redo it. I'm having to say to a kid who's got a C or a B they're pleased with, 'That's not good enough. You've got to do it again.' It's horrible.

"They're under massive pressure and some of them are just switching off: they think, 'Oh, sod it, then – I just won't try.' And some, especially the brighter ones, you can see them struggling. Especially when you get to year 11. There are quite a number of kids now who can't go to the hall for exams because they have panic attacks. I don't remember that happening when I was at school. It's the able girls who seem to suffer the worst."

The school's last internal observation, she says, rated her teaching as outstanding. But she wants to quit. "I feel like I can't live up to what they want," she says, meaning the government. "And anyway, I've got no work-life balance."

History teacher, 28, east London: "I'd say 20% of what I do does not benefit the students. It's just proving I've done this and that; that I know what level they're at and have set them all these targets. I have to do it, but it's pointless: a lot of it will sit in a file and no one will look at it. But everything is just in case. Just in case the inspectors turn up."

It is easy to assume that the crisis in teaching has really only kicked in under this government. In fact, ever-increasing hours, the dominance of targets, the snowballing power of Ofsted and the great academies drive are things that took root in the Blair and Brown years, and there are plenty of ex-teachers who quit when Labour was in power.

One is Theresa Devlin, who was a teacher until April 2010. She lives in Brentwood, Essex and now works as a full-time foster carer, as well as looking after four of her own kids. She went into teaching at 37 – "I was a TA and I'd watch teachers and think, I can do better than that" – and worked at Dorothy Barley junior school in Dagenham, the outer London borough where she grew up.

It was not the easiest job, given Dagenham was becoming the capital's cheapest housing market and its social problems were multiplying. "Parents would come in, no appointment," she says. "They'd eff and blind at you, all sorts. With one teacher, the parent came in with the child there, and said, 'See him? You ain't gotta take no notice of him, cos he talks out of his arse.'" When it came to dysfunctional families, she was at the sharp end: for an extra £1,500 a year, she was in charge of safeguarding: "a massive responsibility" that, among other things, involved referring cases of child abuse and neglect to social services.

A year after Devlin started work, Ofsted put the school in special measures, and the fine details of her job were suddenly dictated by the borough council, via the school's management (aka senior leadership team). She was handed lesson plans from above, and instructed to stick to them.

Former teacher Theresa Devlin: ‘The kids were bored. The lessons were so stale. There was no fun. It was just about improving on things in the Ofsted report.’ Photograph: Jon Tonks for the Guardian

"They actually said, 'Now do this, now say that.' The basis of it was being told exactly what to do. There was a geography lesson I wanted to teach, on 'Connecting yourself to the world'. I got told off, because I contacted someone in America who had the same name as me, and I got my whole class to write to her. We took photos out of the window, sent emails, and she replied. I thought it was great: she was in New York and we were in Dagenham. But I was told it wasn't appropriate because it wasn't what was on the lesson plan.

"The kids were bored. You'd say, 'What do you think of what we're doing?' And they'd say, 'It's boring.' And if you've got a bored kid, that's when the behaviour problems escalate. And they were really bored. The lessons were so stale. There was no fun. It was just about improving on things in the Ofsted report. Nothing else seemed to matter."

What really got to Devlin, though, was the fact that her workload was extending into the distance. "When I first started teaching, I'd work through the week, till 10, 11, 12 o'clock, and weekends were for my kids. Then I started working on Sunday afternoons. Then it was all day Sunday, then part of Saturday as well, you know? And holidays – even in the summer, you'd spend half of it preparing."

The snapping point came when she was called to do jury service, on an attempted murder case. "I had a lunch hour," she says, still marvelling at the idea. "And it was like being normal. And the day I finished jury service, I went into work and they got a phone call saying, 'Ofsted are coming in again.' And it was, 'That's it. I've had enough.'"

Her old school is now seemingly on the way to being converted into an academy, to be sponsored by a private-sector educational organisation called REAch2. At the last count, all 36 of its staff were opposed to the plan. But, as similar cases prove, such things do not tend to count for very much.

History teacher, 40, Lancashire: "In 2010, we were rated 'good' by Ofsted. Results dipped in 2011-12 and we got hit by an inspection. It felt as if they were waiting to get us. And they gave us a 4, 'inadequate', just before the next set of results came in – they'd gone back up, and are predicted to go up again. But we were hit by an Academy Order, and they've chosen a sponsor – before their consultation starts! It seems a set-up."

I meet Phil Brett just before the start of a new term. Since last year, the 51-year-old has been a year 5 teacher at a primary school in Haringey. Between 2002 and 2012, he did a similar job at Downhills primary in Tottenham, a school that eventually became a byword for what the government is doing to education, and the subject of a huge news story.

Downhills, he says, was a typical inner-London primary, with "a whole diversity of races, religions, backgrounds – although predominantly working class or below." The school's ethos amounted to "trying to do the best for these children… reading, writing and maths, obviously, but we were also in a music scheme, where every child in year 4 could take home a violin or cello to learn. And there was an emphasis on art – not at the expense of reading, writing and maths, but… a rounded education, so they wanted to learn, so they weren't just statistics on a league table, commodities. And the staff were together on that, with the parents and children."

In January 2011, Downhills was inspected by Ofsted and given "notice to improve". Changes were made to the way some subjects were taught, and that September another inspection found the school was making "reasonable progress".

And then something unexpected happened. In December 2011, it was announced that the DfE intended to close Downhills and open an academy. Parents led a huge campaign to oppose the plans, supported by teachers and the local Labour MP. But in January 2012, Gove ordered another visit from Ofsted – the secretary of state can do this, though it's very unusual – and a team led by the same inspector who had said Downhills was improving said it was simply "failing to give its pupils an acceptable standard of education".

The school was put in special measures. After that, changes happened quickly: the DfE sacked the entire board of governors, the head resigned and the way was cleared for a takeover by the Harris academies chain, founded by Philip Harris, Tory peer and founder of retail chain Carpetright.

"There were tears in the staffroom," Brett says. "We'd been playing one game, and new rules had been brought in. There was a general feeling that it was a stitch-up, that no matter what we did, Gove wanted us turned into an academy. It was playing politics with children's education."

Primary schoolteacher Phil Brett: ‘You don’t join up thinking, wow – you get 13 weeks’ holiday and the pay’s all right. You join because you want to make a difference.’ Photograph: Jon Tonks for the Guardian

Brett worked for one term at the school that replaced Downhills, the Harris Primary Academy Philip Lane. "They're very keen on corporate image. A plenary session of a big day we had was about private health insurance. Apparently you get up to three operations a year. For me, it was like, 'I don't want to be part of this.' If I'd wanted to join the corporate world, I would have done it."

He has the same complaints and concerns as just about all the teachers I meet: the onward march of the academies programme, ever-changing "strategies", the mountain of paperwork, the sense that teaching the whole child is being reduced to pushing up sets of dry numbers – and an overwhelming feeling that teachers work in the face of tremendous hostility from politicians. "I'm going to sound sappy now," he says. "I'm proud to be a primary schoolteacher. I think it's a great job, and teaching in somewhere like Tottenham, you think there's a point to your job. I won't say we always skip into the staffroom, but you don't join up thinking, 'Wow – you get 13 weeks' holiday and the pay's all right.' You join because you want to make a difference, because it's important, to teach children. And that keeps you there, despite government policy. But shouldn't it be because of government policy?"

All the teachers I meet return time and again to one key argument: that though some of their concerns are about the profession, in the end they are also about the kids they teach. Everyone has anecdotes they say shine light on the contorting effect all those targets and assessments are having on children, and on how the cold, mechanistic teaching methods are beginning to be reflected in the way children don't just work, but think.



Long-serving teacher who now works at a new academy in eastern England: "After my last school became an academy, pretty much all the staff left. Some amazing teachers went. The new ones are Tiggers, all style and no substance. My new school's an academy, too, and there's a culture of fear. Certain people have been… disposed of. If you create scapegoats, people keep their heads down, don't they? No one says a thing, for fear of going in some sort of black book."

Sarah Cumberlidge remembers a taster day her school put on for kids in their last year of primary: "Little year 6s, who came in to do a lesson and try a few things. And afterwards, they said, 'But Miss, what was the learning objective?' I was horrified."

Back at Worle Community school, I talk to three of Nancy Powell-Brace's GCSE drama students. They knock back the idea that it's a "soft" subject: quite apart from all the theory they have to learn, they say it teaches them to be assertive, and supportive, and to empathise. "You have to act out other people's emotions," says Asha Sutton, 14.

How do they feel about the rest of the stuff they have to do at school? "It depends what subject it is, whether they're drilling it into you," says Lucy Jenkins, 15. What subjects does that happen in? "English, maths and science," they say in unison.

"There are just lots of tests," Lucy says. "'You must get to this level, or you'll have to retake it.' You know what you're capable of doing, but sometimes they expect more than your best."

And what does that do to you? "I lose concentration and I mess all of my work up."

"Sometimes, you snap at people," says Yasmin Robinson, 14. "Teenagers go through all these changes anyway, and you've got the stress of that, plus the stress of meeting all these targets."

One Worle student knows only too well the effect this can have. Off the record, she says: "Last year, I was at home for a week because I had a breakdown at school. Because of all my subjects, the expectations and the stress. There were tests coming up, and a mock exam in science that would decide whether I do my exam this year or next.

"You need fun," she says. "It shouldn't be just about the core subjects. You have to have something that's your passion." Then a borderline heresy. "That you enjoy, you know?"

• This article was amended on 14 March 2014. An earlier version said Theresa Devlin worked at Dorothy Barley infant school in Dagenham, when she worked at Dorothy Barley junior school. It was further amended on 26 March 2014 to clarify a reference to a meeting for Harris Federation schools. An earlier version wrongly implied that the main session was specifically about the selling of private health insurance.