A demand and supply review by consulting firm Grant Thornton for the Education Department found autism was the fastest-growing disability in the state, up 21percent in the past four years.

Students funded for autism under the Program for Students with a Disability (PSD) more than doubled from 1946 in 2006 to 4103 in 2010.

The review was prepared last April but was released only last week after a freedom of information request by Western Metropolitan Greens MP Colleen Hartland.

"The majority of students supported under the [autism] category of the PSD are in their primary years, which will place increased pressure on secondary mainstream and general specialist schools to provide for this cohort over the next two years," the report said.

Ms Hartland said the report showed education services for students with autism were failing families in the west.

Autism Angels president Dina Tamburro said the findings came as no surprise to parents in the area. Schools were not meeting the growing need for teachers and aides to be trained in supporting students with autism. The number of students with autism enrolling in mainstream schools has rocketed, from 154 in 2006 to 429 in 2010.

Ms Tamburro said it was important for parents to have the choice of mainstream or specialist schools, but the west still had no specialist school beyond grade 3.

"We're supposed to have this prep to year 12 school in Laverton, but there's still no answer about when that will be. They're not telling us the full story."

Western Metropolitan Liberal MP Bernie Finn said the government remained committed to the Laverton school before the 2014 election. But his priority was to see the integrated disability education and awareness program running at Moomba Park Primary School in Fawkner rolled out across existing schools.