The country's top court has rejected the latest appeal from parents who want their autistic children to receive specialized therapies from Ontario school boards.

The Supreme Court released a ruling on Thursday in which it declined to hear the appeal from the five families trying to sue the Ontario government for discrimination against their children.

As is customary, the decision was released without explanation.

"Obviously, the court's decision today was a letdown for us," said parent Taline Sagharian in a news release. Her 12-year-old son Christopher has autism.

"For almost a decade now, families of children with autism have continued to face an impossible choice between prohibitively expensive private autism programs and an unresponsive public school system."

The families would meet with their lawyers in the "coming days to determine next steps," the release said.

The families are suing the province and five school boards, accusing them of discrimination for failing to provide their children with the expensive therapies they require. They have argued that other kids with special needs receive therapy along with their education within the publicly funded school system.

Therapy costs mount

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

The families filed the $1.25-billion lawsuit in 2004, claiming negligence and damages at the time.

In March 2007, Ontario Superior Court Justice Maurice Cullity sided with the provincial government in striking down several of the key claims, including negligence and damages. But he left the door open for the discrimination claim.

In May, the Ontario Court of Appeal told the families that their case would have to be drastically reworked for it to have any chance of succeeding. The province's highest court said the lawsuit was unclear, which "makes it difficult to know" what the parents want.

With files from the Canadian Press