Heads and teachers often knowingly "dump" their vulnerable pupils in unsuitable and poor-quality alternative education provision, according to the government's behaviour adviser.
Some schools spend up to half a million pounds a year sending disruptive pupils elsewhere because they "may simply want the child out of school on any terms", a new report by Charlie Taylor claims.
The report says that some providers are "brilliant" but others "do little more than keep their pupils off the streets". Mr Taylor said that he had been told that some schools or local authorities are drawn to "cheap" courses and that some pupil referral units (PRUs) are even "outsourcing" pupils to other providers "at a fraction of the price they receive from the local authority".
Last year, education secretary Michael Gove asked Mr Taylor, a PRU headteacher, to come up with ideas for improving the alternative provision (AP) sector. Mr Taylor visited providers around the country that educate children not in school, usually because of exclusion or bad behaviour. Last year, 23,020 pupils were put into AP.
Mr Taylor recommends making schools more accountable for checking the quality of provision and introducing a more academic curriculum into AP.
The quality of education offered to excluded children has long been a concern to Ofsted inspectors, schools and even providers of AP. Headteachers say they find it difficult to judge the worth of AP run by private providers: local authorities are not obliged to vet them thoroughly.
"Bad providers just take the money and run. Some are only a step up from a babysitting service. In many, children don't bother to turn up," one deputy head from North London, who asked to remain anonymous, told TES. "Some schools only make one visit to providers. They have a pupil who is a pain and want to shunt them away. The child's life chances aren't part of the equation. It's despicable."
Anna Cain, head of alternative provider the Boxing Academy in East London, said that schools were being persuaded by slick marketing.
"Some providers show heads a glossy brochure and they think it all looks OK. By the time they find out it's not, it's too late," she said. "I worry about safeguarding - some of these providers have no relationship with the local authority and won't notice if something happened to the child."
Mr Taylor called on the government to set clear standards for schools to follow when using AP. He also said that schools, local authorities and PRUs should come up with systems for checking on the quality of education for children in AP.