Why aren't private schools subsidised?

Posted by MrMrsPotts@reddit | AskUK | View on Reddit | 70 comments

In Denmark, if you send your child to private school you pay the difference between the full private school fee and the amount the state would have paid for your child at state school. That seems fair as you have still paid tax.

Why is that politically impossible in the UK? No party seems to be proposing it.