If a school is not affiliated with the state, government shouldn’t be involved with it at all. If you want to fund the non-public schools then taxation isn’t the appropriate term because it implies the government is the middleman in the transfer of that money. Therefore, funding of the non-public schools should come from something other than taxes. In a perfect world, each taxpayer would have the ability to designate whether they want to accept paying taxes to fund governmental schools, or whether they would rather decline that but pay a monetary amount of equal or greater value toward the school of their choice.