Schools have "too readily" used unofficial, illegal exclusions to deal with pupils that have special needs, inspectors have warned.
Youngsters with special educational needs and disabilities (SEND) are more likely in general to be excluded or absent from lessons than their peers, according to a new Ofsted report.
And an "alarming" number of parents said they had been asked by schools to take their child home, in addition, or instead of suspending them.
Under a new Code of Practice introduced in England three years ago, local areas - including councils and health authorities - have a duty to identify and meet the needs of SEND children, up to the age of 25.
But Ofsted's report found that even in some areas that have implemented this Code well, not enough is being done to deal with school exclusions among these youngsters.
"Children and young people who have SEND were found to be excluded, absent or missing from school much more frequently than other pupils nationally," it said.
"Even in some local areas that had implemented the Code of Practice well, leaders did not have appropriate plans to deal with the levels of exclusion for these pupils."
The report added: "School leaders had used unofficial exclusions too readily to cope with children and young people who have SEND.
"Across nearly all local areas inspected, an alarming number of parents said that some school leaders asked them to take their children home. This was in addition, or as an alternative, to fixed-term exclusions. It is illegal."
Pupils with a statement of special educational need or with SEN support at primary, secondary and special schools in England were permanently excluded on 3,285 occasions in 2015/16, government figures show, while those without SEN were expelled 3,405 times.
SEN youngsters were also given fixed-term exclusions on 158,355 occasions, while those without were suspended 181,010 times.
Around 1.24 million (14.4%) of pupils in England have a special educational need, Department for Education figures show.
Alison Worsley, director of external affairs at Ambitious about Autism, said: "These findings are troubling as they point to a worrying number of schools breaking the law.
"Sadly Ofsted's findings are not surprising - we estimate that 26,000 children and young people with autism were unlawfully excluded last year and as a result denied a basic right to education.
"Ofsted's report highlights the scale of the problem - we now need strong action from decision makers, including a robust reporting system, that will hold schools to account and clamp down on the practice of illegal exclusions."
Children's minister Robert Goodwill said: "Our guidance is clear that any decision to exclude a pupil should be lawful, reasonable and fair.
"While exclusion can be used as a sanction for schools to deal with poor behaviour, permanent exclusion should only be used as a last resort, in response to a serious breach, or persistent breaches, of the school's behaviour policy."
The Government has announced an exclusions review.
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