Children with disabilities face discrimination under equality laws which allow schools to exclude them for "challenging behaviour", a judge has ruled.
Judge Alison Rowley, sitting in the Upper Tribunal, said it was "repugnant" to consider such behaviour as "criminal or anti-social" when it is a direct result of a child's condition and "not a choice".
She made the remarks when ruling in favour of a 13-year-old boy with autism, identified only as L, who was excluded from school for aggressive behaviour.
The judge said schools should not be prevented from excluding children where it can be demonstrated that it is "proportionate" to do so.
But she found that a regulation under the Equality Act 2010, which lets schools exclude pupils for such behaviour without justification, is unlawful and incompatible with Human Rights laws.
The tribunal heard the rule affects "tens of thousands" of children with conditions including autism and ADHD.
Lawyers and advocacy groups welcomed the judge's decision, which they said should give children with such disabilities greater protection.
The boy's parents, who challenged his exclusion by bringing a case against the Education Secretary, said on Tuesday they were "delighted" by the ruling.
"We have always believed passionately that our son and other children in his position should have equal rights to be able to go to school and receive the support they need to achieve the best possible outcomes," they said in a statement.
"L's autism means that he will grow up in a world where he will face challenges and adversity throughout his life.
"School should be somewhere he can go without fear of discrimination or exclusion for actions which he has no control over.
"Knowing that one of the key rules that prevented that has now been found to be unlawful is of great comfort to us, and we hope, many other families."
It allows schools to treat children with a "tendency to physical abuse" as falling outside the protection of the Equality Act 2010.
Judge Rowley said the rule came "nowhere near striking a fair balance" between the "fundamental rights" of such children and the interests of the wider community.
She added: "In my judgment, the Secretary of State has failed to justify maintaining in force a provision which excludes from the ambit of the protection of the Equality Act children whose behaviour in school is a manifestation of the very condition which calls for special educational provision to be made for them.
"In that context, to my mind it is repugnant to define as 'criminal or anti-social' the effect of the behaviour of children whose condition (through no fault of their own) manifests itself in particular ways so as to justify treating them differently from children whose condition has other manifestations."
Polly Sweeney, human rights partner at Irwin Mitchell - who represented the family, said: "We are delighted with this outcome and pleased that the Upper Tribunal has recognised in strong terms that the profound and severe discriminatory impact that these rules have on vulnerable children such as L when accessing education is unlawful.
"As has been made clear in the judgment, this decision does not mean that schools are prevented from excluding children where it is necessary and proportionate to do so.
"However, it will ensure all disabled children are afforded the same safeguards, protections and rights under the law regardless of whether their disability gives rise to challenging behaviour."
Ms Sweeney praised L's parents for their "tenacity and courage" in pursuing the case on behalf of their son and other children with disabilities.
The case, which was an appeal from a first-tier tribunal made in August last year, was supported by the National Autistic Society (NAS) and the Equality and Human Rights Commission (EHRC).
EHRC executive director Melanie Field said: "The level of exclusions of pupils with a special educational need or disability has risen dramatically in the last few years and they are now almost seven times more likely to be permanently excluded than other pupils.
"We funded this case as we were concerned that children whose disability can result in them being more likely to be aggressive were being unfairly denied access to education.
"We are delighted with this judgment which will require schools to make reasonable adjustments to try to prevent or manage challenging behaviour and justify that any exclusion in these circumstances is proportionate.
"This is a positive step towards ensuring that everyone has the opportunity to reach their potential through education and increasing the inclusion of disabled children in mainstream education."
Jane Harris, director of external affairs at NAS, said: "This is a landmark verdict which could transform the prospects of future generations of children on the autism spectrum, by helping them get the education they deserve.
"The Government should recognise this decision and act immediately to make sure that autistic children are no longer unfairly excluded from school."
A Department for Education spokesman said: "The Government is fully committed to protecting the rights of children with disabilities, as well as making sure schools are safe environments for all pupils.
"We will be carefully considering the judgment and its implications before deciding the next steps."
Paul Whiteman, general secretary of the National Association of Head Teachers (NAHT) said: "The decision to exclude a student is never taken lightly and always as a last resort.
"But school leaders do need the autonomy to decide when and how to exclude students to protect the health, safety, education or well-being of other pupils and staff in the school."
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