Don't worry, I'm not suggesting they pay up front. No, the fees will only kick in when they earn, say, £10 per month pocket money. Alternatively, they could be recouped by means of a Literacy Tax.
Of course, there will be some Moaning Minnies who suggest that teaching people to read and write is beneficial to society as a whole, and should therefore be funded out of general taxation. But if we took that argument seriously we would hardly be charging people to become qualified as teachers, doctors, engineers, social workers, scientists, etc., now would we?