Children diagnosed with behavioural disorders may simply need to be allowed to "let off steam", an expert has claimed.
Teachers are 'cynical' about the reported rise in disorders
Professor Priscilla Alderson, an expert in childhood studies at London's Institute of Education, believes conditions such as attention deficit hyperactive disorder and mild autism are being over-diagnosed.
She said many children were 'cooped-up' at home, and not given the opportunity to run off their extra energy in parks and playgrounds.
Teachers backed Professor Alderson's theory, with leaders saying the profession was cynical about the increase in the number of children suffering from behavioural disorders.
The number of children registered with special needs, which covers conditions ranging from dyslexia to autistic spectrum disorders, has virtually doubled in the last decade to 1.4m.
But autism specialists called Professor Alderson's theory "disappointing", and warned her comments would add to the stress and confusion families experienced.
Professor Alderson said many children were simply feeling restless and excitable.
She said she had recently visited a school for children with special needs where 27 pupils had been diagnosed as autistic.
But she told a national newspaper: "Of those, only two that I met displayed the lack of contact and absence of empathy which denotes true autism.
"Money is behind all this. Psychologists want the work and lower the diagnosis threshold accordingly.
"Special needs is an administrative device describing children who have extra needs from those provided for the average classroom."
She added: "Playgrounds and parks are empty, because of the scare stories about abductions.
"But children need the space and freedom to play, run and climb - without that, they are restless and come to be seen as abnormally 'hyperactive'."
Professor Alderson said: "About eight children are murdered outside the home each year, compared with about 50 inside.
"Cooping up children inside homes is not going to do them any good."
Eamonn O'Kane, head of the National Association of Schoolmasters and Union of Women Teachers (NASUWT), the second largest teaching union, said: "A lot of teachers are very cynical about the reasons behind the boom in the numbers of these conditions.
"We need to do more to address the consequences for staff who have to deal with the bad behaviour."
But a spokeswoman for the National Autism Society said: "The importance of receiving a correct diagnosis cannot be emphasised enough.
"Access to the most appropriate education and support depends on receiving a correct diagnosis."
She added: "It is disappointing that reputable diagnosis is being questioned, as this can only add to the stress and confusion that many families face."
She said a NAS investigation had found that teachers believe the numbers of children with an autistic spectrum disorder is on the increase.