The children's commissioner for England has said it is shameful that the country is failing to provide adequately for children with autism.
Prof Aynsley-Green is critical of the treatment of autistic pupils
Sir Al Aynsley-Green - who recently met families with autistic children - said it was "shocking and appalling".
The National Autistic Society says more than half the 90,000 children with autism in the UK are not in the sort of school their parents believe is best.
Sir Al said teachers and schools should be better trained to cope.
"It's appalling and it's shameful for our country, the fifth richest economy in the world, to have so many children that are not being looked after and given the resources they need to develop to their full potential," he said in a BBC interview.
"It is shocking and appalling."
Sir Al said: "In my office last week we had to be very careful about not overloading these children with bright colours, with noise, to have quiet space for them to relax in and to be comfortable in.
"These aren't things that cost large amounts of money. It's a cultural change.
The National Autistic Society has campaigned at Downing Street
"It is a way of understanding the lives of these children and how we can improve it for them."
Ruth McNichol, whose son George has Asperger's syndrome, told BBC News teachers needed to be trained to deal with autistic children.
"There appears to be a lot of ignorance about autism and the particular education techniques that are required to teach children with autism.
"It is particularly bad when children make the transition from primary to secondary school.
Ms McNichol said when her son had started secondary school "he was bullied, he withdrew from lessons in the classroom and the staff didn't appear to know how to engage with him".
"At the end of his first year at secondary school, despite not being in any way disruptive, he started self-harming and he was obviously in a great deal of distress," she said.
It is estimated by the National Autistic Society that there are 90,000 children with autistic spectrum disorders - which affect their social interaction and communication - and fewer than 8,000 specialist places.
A spokesman for the Department for Education and Skills said special educational needs were a government priority.
There had been major increases in education funding and local authorities' budgeted expenditure on special needs had also increased, from £2.8bn in 2001-02 to £4.1bn in 2005-06, with more to come, the spokesman said.
"We will also look at the case for further funding in the current spending review, which includes a specific focus on services for disabled children."
He added: "We have always been clear that inclusion is about the quality of children's education, and how they are helped to learn, achieve and participate in the life of their school, whether that is a mainstream or a special school."
There was good practice guidance for local authorities and schools on meeting the needs of children with autism.