Mainstream teachers are now regularly doing dangerous and unpleasant tasks such as cleaning out tracheotomy tubes and changing nappies.
A report published this week said teachers are being asked to work "above and beyond the call of duty" because schools lack the resources to support pupils with the most severe special needs.
Huge demands are being placed on teachers who lack proper training and could be vulnerable to legal action if something goes wrong, according to the study carried out by Cambridge university academics for the National Union of Teachers.
Problems are greatest in the most disadvantaged areas where schools often face "a critical mass of unmet needs that overwhelms school staff and creates a downward spiral of achievement", the report said.
One primary teacher said: "Our planning takes so much longer - teachers have to ensure there are always two people there at all times in case a child requires medical intervention, such as sucking out the tube or for a child who blacks out." The teacher had not been given medical training and was shown how to use the tracheotomy tube by the child's parents, a situation described by the study as "professionally unacceptable and potentially dangerous".
Another primary teacher told researchers: "We can accommodate some medical problems but some are so severe you can't access the curriculum. It's more like nursing than education."
The 67-page study is based on visits to two special schools and 18 mainstream schools which had shown commitment to including pupils with special needs. It found teachers supported the principle of educating children with special needs in mainstream schools because they thought it was good for them and helped teach other pupils tolerance and respect.
But the teachers were concerned about the lack of support for pupils with the most severe needs, particularly those with behavioural and mental health problems.
Collaboration between schools which could improve special needs education was "undermined by fragmentation of school types (specialist schools, academies, selective schools), competition for pupils and reluctance to accept children seen as detrimental to a school's attainment profile," the report warned.
Steve Sinnott, general secretary of the NUT, said the report showed that the Government needed to conduct a "root and branch independent review of inclusion policies and practice".
"It contains much that is shocking and inspirational at the same time," he said. "The commitment of staff and parents to youngsters with special needs shines out. But many are being let down by inclusion on the cheap.
"The Government must put an end to the stress and strain experienced by teachers, support staff, parents and youngsters alike. In the meantime, there must be a halt to the closure of special schools and government action to amend the education and inspections Bill to protect existing SEN services."
Lord Adonis, schools minister, said: "We put the needs of the child first.
Children should be taught in mainstream schools where this is what their parents want and it is not incompatible with the efficient education of other children.
"Investment in education is at record levels and local authorities are spending more on educating children with SEN - up from pound;2.8 billion in 20012 to pound;4.1bn in 20056. Children with SEN are taught successfully in a range of settings, including mainstream schools, special schools and specially resourced provision in mainstream schools."
Life in a special school,Friday magazine
The Cost of Inclusion by John MacBeath, Maurice Galton, Susan Steward, Andrea MacBeath and Charlotte Page of Cambridge University is available from www.nut.org.uk