A private tutor is able to focus on specific areas that your child may be having problems with. A school teacher will only be able to give limited private attention to students as they are constrained by time and tough targets for subject coverage.
These are extremely important factors to learning any subject. The more confident a child feels with their schoolwork the more creative their thought processes become which means they will be able to grasp complicated concepts much more easily.
Sometimes your child may have missed key points in the syllabus that are now holding them back from understanding the more advanced concepts. A private tutor will quickly be able to identify areas that need work and bring your child up to speed. This is especially important if your child has been ill and missed a few lessons.
A lot of children may be too shy to ask questions in class and may then miss out on key points in their subjects. Like a large rock in a fast flowing river this can have repercussions for a long time afterwards. They are much more likely to ask questions in a one-on-one environment with their tutor.
If your child is struggling with homework the tutor can help! Sometimes they may be asking questions of mum or dad that you just can't answer. Sometimes at the end of a long day in the office you don't want to come home from work to 2 hours of homework help! A private tutor can provide the answers your child needs and the tools your child can use to find the answers themselves.
Your child may only be able to concentrate for 10 minutes before their mind starts wandering onto other things. This is completely normal and almost completely overlooked in the public schooling system. A private tutor will easily be able to recognise when your child's attention span is wavering. A minute or two discussing something else or having a biscuit or a glass of water will reset the clock to an extent and your child will be able to get back on track quickly.