I agree that funding of the Ontario Protestant and Catholic boards is unnecessary - we should only have one school system in the province.
But, your comment on PC funding needs a bit of a history lesson to frame it properly. The public system was historically Protestant, it did not finish it's transition to a full secular public system until late 80's. At that time Catholic school supporters had a portion of their school tax diverted to cover the cost of grade 11 and on. ,
With respect to funding grades 11&12, that was done by the Big Blue Machine at no cost to taxpayers. It simply re-routed catholic supported school taxes elections back to the Catholic system because this funding was never extended when high schools went from ending at grade 10 to ending at grade 13.
It was also a stick in the eye by outgoing PM Bill Davis, who lived across the street from Cardinal Leger Secondary School at the time.