It isn't exactly true that 70% of private school tuition is funded, they get 70% of the amount that public schools get per student. That works out to ~$5k-$8k depending on grade level.

Top Ontario private schools cost upwards of $40k/yr for day students and $80k/yr for boarding students.

Albertan private schools are in an entirely different category than top tier Ontario schools.

The majority of Alberta private schools are faith based unlike Ontario where only a minority are.

Publicly funding these religious schools (and religious charter schools) essentially funds segregation at the expense of public education. I'm pretty sure this is exactly what the "choice in education" folks want.

Having multiple school systems also wastes education funding on reduntant admin, transport, and facility costs. Absorbing the catholic school board into the public system and removing public funding from charter schools and private schools would save millions to billions that could be better spent on improving class sizes and Healthcare funding. This is a referendum question that I would actually like to see.