I'm a staunch secularist, and ideally I would like to see one school system in Ontario. That being said, I think there are a lot of other issues to be addressed before I'd even bother trying to devote my energy to abolishing state funded Catholic education. I don't think you can simply rely on the fact the majority of Ontarians aren't Catholics. Many send their children to Catholc schools because they are seen as instilling better morals than the education system. So a Muslim family sending their children to a Catholic school isn't going to vote for a party that would abolish them. So political support isn't there yet.
The issue of the GSAs and even sex ed. needs to be addressed. Allowing GSAs are a human rights issue and also an issue of the right to freedom of association. Sex ed. is a public health issue regarding unwanted pregnancies and STI transmission. Couldn't a government simply force Catholic schools to comply on these issues using human rights and public health appeals? Its a compromise. Human rights and public health are respected but Catholic schools would still be able to give lessons on Catholic doctrine. I went to a Catholic elementary school. My parents chose to send me there. My parents also taught me to accept homosexuals and to practice safe sex. I'm willing to bet that the majority of parents with kids in the Catholic school system are not fundamentalists opposed to Birth Control and human rights for LGBT people. Now if the government forced Catholic schools to comply, could the Catholic schools take the Ontario government to court on the issue arguing that their right to providing Catholic schooling is being infringed upon? Could they argue that Catholic education is more than simply having lessons in Catholic doctrine? If we could pull something like this off I'd accept it. No it's not one education system, but I'd rather fight poverty and improve people's lives. These are more pressing issues.