Usually I try to have five schools and as many observatories as I can build, but eight school is the optimal number. If you specialize it gives you three for military, three for industrial, and two for philosophy. More than this and you will have schools doing nothing. Also I try to put at least one 4 star researcher per school and if available another gentleman in each. As I run out of techs I close schools and move the gentlemen to the others.

If you have priority research in one field the 4 stars work best and if the schools are close you can shift them for a time.

The best regions for this are the Netherlands, Rhineland, Wurttemberg, and Bavaria. They are all close and have schools at start. Also Saxony and Brandenburg are near by if you like to shift them. You might call this the core area for research and all but two have the slot for observatories.