How many hours a week is good for tutoring?

One to two hours per subject per week. One keeps a child ahead; two is normal when catching up or preparing for boards. Above three hours a week in one subject the returns fall off sharply — tiredness sets in and the independent work that consolidates it gets squeezed out. If a child seems to need more than that just to keep up, the problem is usually not the number of hours, and I will say so rather than sell you more of them.