I already pay a huge amount in taxes and I would resent having to pay to use the state system without a significant tax rebate.
My current personal circumstances allow me to send both my children to a private prep school. I would however, consider paying for a state education on top of the tax I already pay only if the state school was up to the standard of the equivalent private school of my choice.
I would also expect the state school to be selective and account to me for the money I am spending in the same way as the prep school does. If it was not in a position to provide me with the same or better then there would be no incentive to pay. The bottom line is that I would want my monies worth.
FWIW I think the proposal is ludicrous and that it will create an even bigger divide.