No, because they will end up paying for both their kids' education and someone else's, just like American parents are forced to do if they choose a private school.
They should simply demand respect for their constitutional rights, and if Canada wishes to instead privatize its school system wholesale, then it is for the much ballyhooed democratic system to decide, not for the bishops alone.
Standing up for their constitutional rights is a fine thing, but in the meantime it’s not acceptable for a school operating under the aegis of the church to be teaching gross error as truth.