Canada's highest court will not hear an appeal from a group of Ontario families fighting to have the government pay for specialized treatment for their autistic children.

The 28 families argue that costly Intensive Behavioural Therapy should be covered by the provincial government and included in schools across the province.

"This is very, very frustrating for us," Tammy Starr, one of the parents involved in the case, told CTV News.

Victoria Tremblett, whose five-year-old son Jacob is autistic, did not hold back in her anger at the decision.

"They sit behind a desk and they make laws and make rules, and they don't know what it's like," she said.

As is typical in leave-to-appeal rulings, the Supreme Court gave no explanation for its Thursday ruling.

According to the Autism Society of Canada, autistic people can find difficulty in social interactions, communicating with others, and learning in a normal educational setting.

However, symptoms of the disorder can vary wildly from person to person. Some patients display repetitive behaviour and can even suffer from self-inflicted injuries.

Treatment costs tens of thousands of dollars -- sometimes an entire year's salary.

Parents often have to keep their autistic children at home -- away from school -- to receive treatment. Lawyer Mary Eberts, who represents the 28 families who took their case to the Supreme Court, said that amounts to discrimination.

"The public school system does not have its act together. These autistic children are denied a free public education that's available to all the other children in Ontario," Eberts told CP.

"So far, in spite of every effort by the parents, there remains a very strong policy barrier against ... adequate services to children with autism in the public school system."

Taline Sagharian, who has a 10-year-old autistic child, said intensive behaviour initiative (IBI) is far too costly for most families.

"Parents who can't afford to pay for it, they can't provide it for their children, and their children are not progressing the way they could be, and they should be."

She said some families are paying as much as $74,000 for IBI.

Ontario currently offers the Autism Intervention Program to help pay for IBI. However, there is a waiting list of about 1,000 children, and some have been on the list for years.

The program also doesn't cover the entire cost if families get funding for a private service provider.

"But the other issue -- a very, very big issue -- is that the families cannot get this intervention in the schools," Sagharian told CTV.ca on Wednesday.

Education Minister Kathleen Wynne said Ontario is hoping to offer another form of therapy in the classroom, called Applied Behaviour Analysis (ABA).

Wynne could not say how long parents would have to wait for the ABA initiative to begin.

"ABA is the approach that allows kids on the autism spectrum disorders to be part of the mainstream classroom, to be part of the mainstream school," she told The Canadian Press.

"Will we have it implemented by Labour Day in September? No, but the expectation is that there will be more service available and more ABA in place across the province."

Sagharian said Ontario is far behind Alberta, where therapy for autistic children is both readily available and paid for by the government.

With a report from CTV's Roger Smith in Ottawa