It is the staff, primarily, that you are buying. You will probably get a list of staff and their credentials with the prospectus. You can investigate them further when you visit the school; and you can see what impression they made when the school was last inspected by reading the inspection report. What do you think your child will make of the staff, and how interesting would you find them? What is the male:female ratio? Which departments have the largest teaching staff? How old are they (or how old do they seem)? The average staff:pupil ratio is about 1:11, but this varies a lot and you are probably more interested in the teaching groups.