THe purpose of tutoring is to aid and guide and motivate children (and adults) into learning, understanding and developing their knowledge.
If a parent organises tutoring, whether for maths, literacy, science, history, the arts, whatever, it is because they have identified that either their child struggles with certain aspects, or is working ahead of their peers and bored at school and want to ensure their child stays motivated.
They dont have to be tutored to pass an exam, this doesnt help them in the long run anyway, but tutoring can guide children into how exam questions are asked, to identify that you need to search through the question and pick out the relevent information, to make sure they do read the questions properly etc. This will help all students throughout their schooldays. (These are areas that dont seem to be taught in primary school because most tests seem to be tick boxes)
I cant see the point in pushing a child to pass an exam to get into a school if they are struggling, because they will struggle continuously at school, unless the child just needed waking up again after months of being demotivated at school.
HOwever, I firmly believe that tutoring does no harm whatsoever to review and revise the knowledge that children should have learnt at school. Quite often there are huge gaps and tutors can fill in these gaps or identify where a child is struggling and work on those areas.
Tutoring doesnt need to be expensive. There are online options that are just as good and if you structure your time to do a small amount of an activity either every day or once a week, regularly, then children can also learn this way.