Well, with most tutors the offer is that you pay them and they’ll spend an hour (or however much time you have bought) plus preparation time to teach your child.
however like reading, maths is best learnt little and often. If your small child is having trouble with reading then usually the best advice is more practice rather than tutoring.
tutoring can be very effective if it’s focused strongly on those specific areas your child needs to improve on and if it goes alongside your child doing homework either from the tutor or from school.
if you want your child to improve:
then after their year 10 mocks they will be given a list of topics from their exam paper. This will usually be coded red amber or green.
Green on a topic means he could answer the questions. So don’t bother practising those topics any more.
amber means he got some marks on that question but not all of them. These are topics he or you need to tell the tutor to focus on - he’s got some understanding and with help can get more marks.
red topics he got completely wrong.
as the maths exam generally goes from easy questions at the beginning to hard ones at the end either he or you should let the tutor know the red questions towards the beginning because those are the easier topics.
the tutoring can then focus on the topics that will help him pick up as many marks as possible.
there are also a lot of practice sets of questions and revision guides out there - if your son is currently getting a grade 2 he might find some of these useful:
https://stpaulsmaths.com/gcse/revision/
https://corbettmaths.com/5-a-day/gcse/
(the numeracy ones are aimed at grades 1/2/3 and the answers are also on the website).