You thinking of anyone in particular, Alex, with so few students?
I would support what Alex says. From what I know (and I have given private tuition to students from many distance-learning courses, and students strugging to pass after full-time) all the groundschools mentioned so far here are good. There are others that are (or, in two much-missed cases, were) good.
However trust statistics as you would trust Gordon Brown - i.e. don't!