In EB schools don't per se reduce corruption, ie. they don't give law bonuses directly. In the other hand, characters staying in city supplied with a school have a certain possibility of obtaining a law boosting traits. So in a indirect way schools can give law bonuses. Of course if the character is an uncharismatic idiot schools don't help and might even give bad traits.

If schools would give law bonus, there would be a reason to build them in a non governed town, and it would be quite easily rationalized why schools would give law bonus as they educate lawyers, tax collectors, teachers, scribes, mathematicians and many other people associated with governing a city, in addition to FMs.