National Union of Teachers conference votes to oppose use of unqualified staff – including former soldiers and police officers – to cover lessons

Bouncers, ex-soldiers and former police officers are being brought into schools to provide "crowd control" and cover absent teachers' lessons, a teacher has revealed.

One school, thought to be in London, employed two permanent cover teachers through an agency for professional doormen, the National Union of Teachers annual conference in Cardiff heard today.

Bouncers, who more usually work nights keeping order in pubs and clubs, are being employed in schools because they are "stern and loud", said Andrew Baisley, a teacher at Haverstock school in Camden, north London.

"I know of bouncers being employed specifically because they are bouncers to cover lessons," he told the conference.

Recruitment agencies are advertising for people with "ex-marine, prison officer, bouncer, policeman, fireman" backgrounds to become supervisors, who do not need to have any teaching qualifications to oversee lessons.

It comes as ministers prepare to unveil the final part of a major review of children's behaviour this week which will call on governors, headteachers and parents to support teachers when they discipline pupils.

Baisley said some schools seemed to believe the job of supervising a lesson was about "crowd control and childminding; if you're stern and loud, that's what's necessary to do the job", he said.

"The problem is, we need someone who's trained with children, to be able to interact with children. If someone is away, you don't want any teacher, you want a teacher from that particular subject so they can help the children with their work, so that the whole hour isn't a complete waste of time."

The school Baisley knew of, which he refused to name, had recruited the pair last year. One was subsequently dismissed over "disciplinary offences" which Baisley did not disclose, while the other is still in post.

He said job advertisements for cover teachers regularly appealed for people from military backgrounds or with police training.

One recruitment agency, Aspire People, is advertising online for "hard-core cover supervisors" to fill posts in Birmingham.

The advert, dated 10 March this year, says: "Are you looking for a career change? Look no further! Aspire People are on the hunt for dynamic, inspiring, hard core cover supervisors? What are we looking for? You might be an ex-marine, prison officer, bouncer, policeman, fireman, sportsman, actor or you might be an overseas teacher looking to get some experience in the classroom. Whichever it is we need someone who thinks they can get involved in a school environment and control the kids in schools."

Official government guidance dictates that anyone can cover a lesson, providing they pass security checks. Schools commonly ask other teachers to cover classes, use teaching assistants who have classroom training, or employ dedicated cover supervisors who do not necessarily have training.

Where non-trained staff are used, a senior member of the department would set the lesson up and leave the supervisor to oversee it.

From September, new rules will limit the amount of cover that teachers can provide for one another, meaning schools could become more reliant on non-qualified staff, the NUT said.

The union today voted to oppose the use of unqualified staff to cover lessons. Members also agreed to campaign for a reduction in class sizes to 20 and a guarantee of time out of the classroom for teachers to prepare lessons.

A spokesman for the Department for Children, Schools and Families said: "Heads should ensure that the people they employ have the relevant experience and training – and that all the proper checks are carried out on anyone working with children. Our guidance is clear that cover supervision should only be used as a short-term solution, to provide continuity when the regular teacher is unavailable. Pupils should continue their learning through pre-prepared lessons and exercises supervised by support staff with appropriate skills and training. It is up to heads to determine the best systems for cover in their schools.

"The days of teacher shortages are over. We now have the highest number of teachers in a generation and more support staff than ever – including established members of the school team who can take on cover supervision."