Ontario's funding of Catholic schools violates the charter and should be stopped, a Toronto woman is arguing in a court challenge the province will try to shut down today.

Reva Landau doesn't agree with some of the church's teachings, and is arguing that it infringes her freedom of religion to help foot the bill for its schools.

"They're entitled to have beliefs I don't agree with," she said in an interview.

"There are many people who have beliefs I don't agree with. But these beliefs are being funded with my tax dollars."

The Roman Catholic school system gets about one-third of Ontario's $24-billion education budget, but only 23 per cent of electors direct their education taxes to separate schools.

The case, launched in December 2011, is scheduled to have a court hearing Wednesday on an Ontario government motion. The province wants the challenge dismissed, in part, because it says Landau has no standing to bring it.

The Canadian Civil Liberties Association is intervening in the challenge and is supporting Landau.

The idea for Landau's constitutional challenge first came in 2007, when during that provincial election campaign then-Progressive Conservative leader John Tory proposed extending public funding to schools of other faiths.

"I disagree with that, as I said I'm a public schools supporter, but at least he was trying to be fair," said Landau, a retired non-practising lawyer.

"He was trying to be egalitarian to at least a limited extent…The more I thought about it the more it just seemed unfair."

Public funding of Catholic schools infringes the charter, Landau says, but first the court must find that the charter even applies to the funding formula.

A section of the constitution states that no law can affect the rights of denominational schools and that has been interpreted as making it immune from charter challenges, Landau argues.

It contradicts the charter and was never intended to confer privilege on Roman Catholic education, she says.

"The only way to reconcile this difference is to interpret (the section) as narrowly as possible so it guarantees the separate school system only those rights which clearly existed at the time of Confederation," she wrote in her challenge.

The section was meant, in 1867, to protect rights of a Catholic minority in a largely Protestant schools system, the civil liberties group says.

Interpreting it today to shield separate school funding from charter scrutiny "only serves to erode those very principles," the group wrote.

The Supreme Court has considered the issue and related cases on several occasions, but its precedents should be revisited, the group argues.

The charter does state that nothing in it takes away rights or privileges in the constitution with respect to separate schools. Landau suggests it is redundant.

She is asking the Ontario Superior Court of Justice to order that the government stop funding Catholic high schools and only fund Catholic elementary schools to the extent they were funded in 1867 at the time of Confederation.

That would amount to being funded with "only property taxes from Catholics who declare themselves to be separate school supporters and who live within three miles of a separate school, and property taxes from wholly Catholic owned businesses," Landau wrote in her challenge.