There is a crisis of "epidemic proportions" in education for children with special needs, teachers have warned.
Schools are at "breaking point" with a lack of funding, and no places in special schools, or alternative education, according to the National Education Union (ATL section).
Delegates at the union's annual conference in Liverpool argued that action is needed to highlight the issues faced by "invisible children" and their families.
Proposing a motion on the issue, which was passed by delegates, Emma Parker from the union's Durham branch, said: "The crisis in Send (special educational needs and disability) has reached epidemic proportions.
"Children and their families are in crisis. There is no money, there are no places, there is no support."
She argued that official figures show that there are around 8,000 children with special educational needs plans (Education and Health Care Plan) or statement of SEN that do not have a place in an educational setting.
The figures indicate that this covers youngsters who are "educated elsewhere", outside of schools, alternative provision and further education, and includes those where arrangements have been made by their parents or local authority, and those awaiting a place.
"I believe this is just the tip of the iceberg," Ms Parker said.
"What about the children who are on reduced timetables? What about the children who are receiving two hours a week of tutoring?
"These children are not counted in these numbers.
"These children also deserve a full and balanced curriculum where they can thrive."
The resolution, entitled "invisible children", argued that "every children is entitled to an education and that no child should be forgotten".
It goes on to say that across the UK, "there are a growing number of children who are on a reduced timetable within school, are excluded from extra-curricular activities and are not being allowed to access a broad and balanced curriculum, receiving little or no education, owing to their social and emotional difficulties".
It adds: "Schools are at breaking point, CAMHS (child and adolescent mental health services) funding has been decimated, and there are no places in special schools and alternative provisions."
The debate came as a straw poll conducted by the ATL section found that many parents with children that have special educational needs and disabilities (Send) say that their youngsters are not in school full time.
The survey, which questioned 444 mothers and fathers, found that 24% say that their child is not currently attending school at all, while 59% said they attend full-time and 9% say they attend part-time.
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