Home tutors have a track record in enabling people to really make strides in a subject. In a class there is always the problem where individuals are glossed over, no matter how good the teacher is. This is typically down to an incompatibility of the teaching method with the student, so changing this dynamic can really bring about a significant upturn in fortunes while also ensuring that the student is enjoying the process. When it comes to personal tutors however, results must speak for themselves. There must be an increase in the grades or the entire process will be for nothing, so those teaching schools that can boast a high percentage of grade increases will allow you to see where the issues lie. If the schools is achieving above 80% of all students increasing their grades by one, then they are likely to be a very good option. For those who fail to see an increase, it may well be that there are other factors such as an incompatibility with the subject or another underlying reason. If the school also achieves an increase of two or more grades of over 50%, they will be highly recommended, since with the proper amount of effort grades could be significantly higher.
The better schools will also be able to monitor the quality of the teaching they are offering by working strictly to the clients wishes. Quality cannot often be assured by agencies that simply employ freelance tutors and assign them randomly.