OK, so in the real world there are often things not going right in school.
Firstly, no one can doubt the importance of a good teacher, but good teachers leave or the good teachers get ill or good teachers may go on maternity leave.
Then you are left with the replacement teacher. For planned changes this should be no problem but often getting a great replacement takes time, but for your child there is only one first chance. Teaching is heavily concept based. Yes you can "learn" it from a textbook but to get good marks you need to understand it and understanding needs someone to explain when you don't. We guarantee that your child will understand every concept in their course. We have the time and the expertise to explain, re-explain and overcome misunderstandings caused by the lack of a teacher.
OK, so the teacher is good, but what if your child has been ill or changed schools and they are behind (or in front) of the rest of the class?
The one to one approach of a good tutor means that we can design a specific catch up course over an agreed period to get the student back to the same position as the rest of the class as quickly as possible.
If the situation is the opposite and the student is coasting because the class is a long way behind them then we can design enrichment sessions that deepen the subject knowledge without intruding on the school's approach. Often schools WILL set extension work but this is often solo work without the interaction and explanation needed. We have time to give that one to one care and the knowledge to see how and where to deepen the knowledge without confusing what is coming next in class.
Finally, you may be told by the school that your child is not quite "A*" material (or is "C" material) and you are not happy with this.
Schools have to be realistic and generally they have to make quick decisions too about resources. In addition modern competition between schools means that it is bad for a school's reputation to put a student into an exam that they fail or do badly in. We have the necessary time to work out what exactly is stopping your child achieving well. Any good teacher in school could do the same, but they don't have time. Even extra classes in school are rarely one-one which is what is needed. Often we find that a poor student is either bored, missed some important idea, had an off day in an important exam or just didnt get it! We can redress this situation because we have time and the expertise to find out what is causing the problem.
We cannot make someone into an Einstein, but achieving well in public examinations doesnt expect an Einstein just a hard working student who understands the material well.