How often should I have a private tutor?

This needs to be a balance between your child’s needs, your tutor’s availability, and your own budget.  For one subject, once a week is probably enough, with your child doing some practise on their own in between sessions. If you are having a private tutor for more than one subject, you should consider one hour a week per subject. However, tutors will understand that this is not always possible and it should be possible to split an hour session into, for example, half an hour of maths and half of English.