The manual addenda has a lot of that -- all the starting spells for instance. The refrence guide (RC1) has all the princial schools. Check out http://www.dominions-2.org/files.htm
Most of nation specific spella sare spell that can be avaible to every-one just researching in the appropriate school (like c'tis terror): so I think these belong to the school that make them normal avaible ... I don't know about (uf there are any) spelss that are only nations-specific ...
I believe that all the national spells that are available to all nations are in their proper school. The others (all summons I think) might not be found in any school. I tried AE Ermor's summons on a Conjuration 20 site and got no bonus from it. It is possible they're in enchantment, though.