The obligation to pay taxes is a general one. In general, tax receipts go into the ‘Consolidated Fund’ and taxes are not earmarked to any particular purpose.
I do appreciate that not all taxpayers make direct use of every service provided by the government, and that parents who choose to educate their children at home are one example of this. However, a similar argument for a tax refund could be made by anyone who does not use a publicly provided service, or some aspect of that service, including those who are not parents. Primary and secondary education is primarily funded through general taxation, irrespective of usage, and not through charging users.