Evidence about the scale of the problem, published by the commissioner today, found that schools have been illegally excluding pupils because they do not know the law.
The commissioner's report included a survey of 1,000 teachers that found 6.7 per cent of schools had sent children home illegally and 2.1 per cent had recorded pupils as being "educated elsewhere" or "authorised absent" when the school had actively encouraged the child not to return.
When asked about the legalities of falsifying attendance records, 24 per cent of teachers said they did not know the law and 31 per cent were unaware that it was illegal to encourage a parent to educate their child at home.
Commissioner Maggie Atkinson said the majority of illegal exclusions were due to “low-level, persistent bad behaviour” and most occurred in secondary schools.
She said school governors should play a key role in ending the practice and called on the Department for Education to empower governors to challenge head teachers over informal and formal exclusions.
“When I stand up in front of a group of educationalists anywhere in the country and say, ‘does illegal, casual and informal exclusion take place in your area?’, the whole room says, ‘absolutely, yes it does’," said Atkinson.
"Because it’s illegal, it’s hugely under-admitted to.
“Governing bodies that have uncovered illegal behaviour should have the right and the duty to sanction the head teacher to make it clear on their disciplinary record that this has been uncovered and is unacceptable.”
Atkinson's report said local authorities and the Education Funding Agency were not doing enough to address the issue, and suggested that Ofsted increase its efforts to identify illegal exclusion practice during school inspections.
Emma Knights, chief executive of the National Governors’ Association (NGA), backed the report’s recommendations for governors.
“While some governing bodies are not willing or able to challenge head teachers, others do it extremely well – we need to equip other governing bodies to do the same,” she said.
The commissioner's report also uncovered evidence of children with special educational needs (SEN) being illegally excluded because schools could not cater for their needs.
The teachers' survey suggested that 2.7 per cent of schools have sent children with SEN home when their carer, classroom support or teaching assistant was unavailable.
The charity Contact a Family said the findings confirmed its own research.
“For disabled children who already need more support than their peers, this withdrawal of education is having a devastating impact on their progress and attainment, as well as their mental health,” he said.
“Parent carers of disabled children told us that illegal exclusions mean they are unable to work or are forced to take a lot of time off work.”