TORONTO - Parents fighting to have their autistic children receive specialized therapies within the public education system go before Ontario's highest court on Monday in an emotionally fraught case that has huge financial stakes for both the families and taxpayers.

Described as a "make or break'' day by one parent involved, the five families are trying to sue the Ontario government and seven school boards for negligence and damages, accusing them of failing to provide or properly fund the expensive therapies in schools.

Known as intensive behavioural intervention and applied behaviour analysis, the therapies for the poorly understood neurological condition that causes developmental disability and behaviour problems can cost between $30,000 to $80,000 a year for each child.

"Families go to extremes,'' said Taline Sagharian, of Richmond Hill, Ont., whose 11-year-old son Christopher is autistic.

"Six years ago, we had to sell our house. We've cashed in our investments and any assets that we have . . . and we continue to go through financial problems.''

In 2004, the families filed a $1.25-billion lawsuit, which has yet to be certified as a class action, arguing their children were victims of discrimination because other kids with special needs receive both therapy and their education within the publicly funded school system.

Last March, Ontario Superior Court Justice Maurice Cullity sided with the provincial government in striking down several of the key claims, including negligence and damages.

However, he let stand the discrimination claim and in later dismissing the province's demand for $85,000 in legal costs, Cullity recognized the public importance of the issue, giving hope to the families that they might still have a case.

The plaintiffs are hoping to persuade the Ontario Court of Appeal during Monday's one-day hearing that they should be allowed to sue for damages if their class action is eventually certified.

The government, based on previous court rulings, wants the entire case tossed.

Toronto lawyer David Baker, who is acting for the families, calls it unconscionable the parents are faced with what they view as a stark choice between therapy and education for their kids.

"In our education system, there is no other group receiving therapy -- whether it's in a hospital, in residential treatment, any form of treatment you can name -- who is deprived of an education,'' Baker said.

Some Ontario families have moved to Alberta or B.C. where autistic children can receive both, he said, while autistic children in the United States are able to access the therapies through the education system until the age of 21.

Education Minister Kathleen Wynne said last spring the province was working to roll out applied behaviour analysis in schools across Ontario, while intensive behavioural intervention would be used outside schools.

In the election campaign in the fall, the Liberal party pledged $10 million for schools to deliver IBI therapy if re-elected, but the plaintiffs argue the McGuinty government has broken its promise.

An estimated 50,000 children and 150,000 adults in Canada have autism, which has been the subject of several legal battles across the country, most unsuccessful.

In the interim, the financial struggles continue for Ontario families with autistic children.

"I find it extremely difficult to watch the other kids on our street hop on the school bus in the morning and go to school while my son has to stay home,'' Sagharian said.

"It's difficult enough to raise a child with autism without having to fight for his basic rights.''