Autism is a lifelong developmental disability which impairs sufferers' social interactions, communication and imagination.
The researchers found that a group of children who received two years of intensive tutoring had higher IQs, more advanced language and better daily skills than similar children receiving standard educational provision.
Early intensive behavioural intervention (EIBI) involved specially-trained staff and parents teaching children a wide range of skills in their own homes for 25 hours a week.
Lessons were broken down into steps and children received constant rewards and praise for their success.
IQ increased for two-thirds of the children and rose "very substantially" for more than a quarter of them. One child moved from having an IQ of 30 to 70.
In north Wales the EIBI techniques are being applied with children with autism in a unit attached to a mainstream school and the project has been evaluated as "outstanding" by education inspectors Estyn.
Professor Richard Hastings from the School of Psychology at Bangor University, one of the researchers, said that the results were "very encouraging".
"EIBI techniques are well-suited to the classroom, and can be used to support access to the national curriculum for children with autism," he said.
"We believe that carrying out these interventions in a mainstream school setting also has considerable advantages, especially because of the opportunities to develop communication skills, social relationships and integration into the full life of the school."
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