All the schools something. Storm- storm snake, ice- frost giant, balance- that judgment angel. It just depends on your level. Again... ALL of the schools summon. The things is that you have to find it out.
In all schools you get a quest from your teacher gives you quest to get new spells and sometimes you have to get a monster (i am a lvl 38 fire wizard) such as at lvl 38 you sumen a phoenix in old town fire cat ally or you also sumen a fire snake in unicorn way. Other wizard can see these monsters come that is all you saw