Is your child’s tutor helping your child to understand the subject better? Or is your child only gaining enough knowledge to pass the next test, only to have to learn it all over again before the next test?
Actually, this is largely up to you as a parent. Your brief to the tutor does a lot to determine how much your child learns. If you want exam preparation, you will get exam preparation. If you want your child to gain actual understanding, you need to ask for that directly.