We recommend 20 hours of tutoring. From research that we have undertaken we have found that with 20 hours of 1-1 tutoring student improved their grade outcome by x2.5!
Each student is unique, working towards their own goals at their own pace. How many lessons you require will depend on what you hope to achieve academically, how far you are from reaching your target grades and how hard you work with your tutor.
Students usually have one or two lessons a week to keep on top of their studies.