You may not have heard of slow education but you probably know about the slow food movement, founded in Italy in 1986 and hugely popular worldwide. Slow food is the opposite of fast food: it promotes local ingredients and traditional cooking in place of processed ready meals and takeaways. After its success, along came slow fashion (buy clothes that last), slow TV (spend hours watching a boat drift down a river) and so on.

To learn about slow education, I go to see Mike Grenier, a 49-year-old English teacher at Eton who founded a UK movement to promote it in 2012. “Slow education”, Grenier explains in his disappointingly modern and nondescript Eton classroom, “means developing lasting relationships between student and teacher and between student and learning”. It means more time for discussion, reflection and learning in depth, he says.

“At the moment, we’re giving them packaged subject syllabuses and feeding them bite-sized dollops. It’s like a GP handing out pills. When you’ve taken them all and completed the course, you’ll be ‘better at’ whatever subject it is. Children from age four to at least 18 are required to prove themselves on a series of tests. It is a very impoverished view of what human beings are.”

Slow education means cutting down on curriculum content. “The total sum of knowledge we now have on most subjects is enormous. Think of biology and the developments in genetics and neuroscience over the past 25 years, or physics and the increased understanding of quantum theory and how the universe works.

“It’s all being crammed into syllabuses and it’s reached saturation point. Teachers say to students that ‘we have got to get through it’. The generation we are teaching now will live to at least 85 or 90. Why are we in such a hurry?”

The idea of slow education was developed in the US early this century by Maurice Holt, who headed a pioneering comprehensive in Hertfordshire in the 1960s and later moved to the University of Colorado. He and Joe Harrison-Greaves, a musician and creative education consultant in the north-west, were among those who helped Grenier found the UK’s slow education movement.

Holt argued that, just as it was “better to eat one portion of grilled halibut than three king-sized burgers”, so it was “better to examine in detail why Sir Thomas More chose martyrdom than to memorise the kings of England”. He was reacting to the worldwide growth in what he called “standards-driven education” and “test-shaped knowledge” – all of which has increased in recent years, thanks largely to Michael Gove’s curriculum and examination reforms.

Does slow education mean returning to “learning by discovery”, “child-centred education” and other 1960s ideas? “No,” Grenier replies with a slight shudder. “Some of the fundamental tenets of slow education are conservative.”

He argues that slow teaching should be underpinned by a version of the classical “trivium” described by Plato, comprising the basics of language, thought and analysis, and communication.

“It’s not throwing everything up in the air and having a Woodstock-style let-it-all-hang-out. There are times when the most effective way to convey concepts and ideas is to use direct instruction and put things up on a whiteboard. Give students five, six, seven key concepts that they really need to know and then, because they can keep returning to these, it is easier for them to explore.”

The stereotype of child-centred learning, he says, is that “you say to students: here’s Romeo and Juliet, tell me what you think of it”. It’s better, he says, first to introduce basic concepts of Shakespearian drama such as tragedy.

So where does he stand on the “knowledge-rich” curriculum currently in vogue? “Knowledge-rich is clearly better than knowledge-poor but it is how the knowledge is used that is critical.” He wants his pupils to learn what a sonnet is, but also to explore how the form can be used effectively.

How much slow education goes on at Eton? “We nail down the things we have to do, while also taking every opportunity to do things in new ways. Because we are a boarding school, students have a huge amount of additional time to do independent reading and show self-motivated love of a subject or skill.”

Grenier, whose father was an investment manager and his mother a teacher, was a pupil at Eton before he went to Oxford. After leaving university he intended to take a course in teaching English as a foreign language but, “covering bases”, wrote to about 25 schools in England to tell them he was “keen on teaching”. Eton offered him a term as sabbatical cover – and there he still is 25 years later. To most of us, it may seem extraordinary – but not perhaps at Eton where, until the 1940s, pupils were taught almost exclusively by old Etonians.

So is Grenier (whose son is also an Eton pupil) living in a bubble? Is slow education just a luxury, affordable only at schools where pupils have so much economic, social and cultural capital that they will succeed however you teach them?

He says he is closely involved in Eton’s outreach programme and works in a variety of state schools in the Thames Valley.

With Harrison-Greaves, he helped set up a network of schools that have explored introducing slow education in largely working-class Lancashire towns, such as Blackburn and Rochdale. He says that School 21, a free school opened in a deprived area of east London by Peter Hyman, a former Tony Blair aide, also embodies slow education ideas.

But can he convince the mass of middle-class and aspirational working-class parents, desperate for their children to acquire certificates that will propel them into professional careers, of the merits of slow education?

“More often than not,” Grenier replies, “parents want their children to be happy at school as well as to achieve. But we have a system that separates those things. It measures how well schools are doing in terms of numbers but it doesn’t take account of personal and social development.”

Shouldn’t he set up a slow free school? “That’s not a plan at the moment. They’re not really free. To set one up, you’d have to tick so many boxes that you wouldn’t want to tick.”

So how can slow education move forward? “We need a royal commission into our education system,” he says. I point out that royal commissions are out of fashion – none has been set up this century – mainly because they take so much time. “It should be a slow process. There’s lots that needs to be thought about: what we now know about child development and how the brain learns, children’s mental health, the effects of social media and so on.”

I admire Grenier’s refusal to be rushed. The economist Milton Friedman started preaching the virtues of free markets in the 1950s; governments finally embraced his ideas in the 1980s. I have a hunch Grenier’s time will eventually come.