More than half of teachers responsible for special needs in mainstream schools say colleagues' attitudes are an obstacle to inclusion, inspectors have found.
A report by the Office for Standards in Education said that too often pupils are taught in isolation or join lessons tailored for the needs of others, leaving them to rely on a teaching assistant.
"The teaching seen of pupils with SEN was of varying quality, with a high proportion of lessons having shortcomings," it said.
Although more mainstream schools now see themselves as "inclusive", there has been little change in the number of pupils with statements in the mainstream. The report said that the Government's drive to integrate special needs pupils has had limited impact and progress towards inclusion has slowed.
It also found, the policy has not led to a reduction in the number of special schools.
Inclusion of pupils with social and behavioural difficulties is proving particularly difficult. The report said even heads committed to inclusion were reluctant to take such pupils, especially where they had attended other mainstream schools without success.
Teachers' leaders said that mainstream schools should not be expected to take children with the most severe behaviour difficulties.
Dr Mary Bousted, Association of Teachers and Lecturers general secretary, said: "If a child with special needs is to be educated in a mainstream school, it is essential to ensure that it is the appropriate place for them." Dr Bousted called for better training and funding for special needs work.
Virginia Bovell, co-director of autism charity PACE and mother of a child with autism, said: "Ofsted has confirmed our suspicions that many children with complex needs such as autism just aren't being catered for by most mainstream schools."
The Disability Rights Commission described the lack of progress towards inclusion as disturbing.
Ofsted's findings are based on inspections and visits to 115 schools to look specifically at special needs teaching.
Forthcoming research for the Department for Education and Skills will show that inclusion can boost the achievement of all pupils. David Bell, chief inspector, said: "Until more is expected from the lowest-attaining pupils, improvements for pupils with special needs ... will be slow."
The report is the most comprehensive look yet at the impact of the Special Educational Needs and Disability Act 2001, which gives parents the right to demand a place at a mainstream school as long as that does not damage the education of others.
A Government spokesman said: "We welcome the publication of today's report as it shows that more mainstream schools than ever before are inclusive and want to be seen as such."
* set high targets
* increase expertise by developing partnerships with special schools
* use comparative data to monitor and analyse the performance of special needs pupils
* involve all staff in planning for special pupils not just specialists
* do not be afraid to adapt curriculum to meet needs of special needs pupils
* use teaching assistants to support special needs pupils but do not use them as a substitute for planning lessons that meet children's needs