Why not do as it is in (for an example) Baldurs Gate, you don\'t get experience for killing a summoned creature, besides you must make a difference between summoning and raising spells, and the high level monsters maybe need to be bribed or such to join your side.
And raising spells, which is black necromantic spells need a corpse of some sort to work, if you raise a newly killed person or monster you get a zombie and if you raise a body from a cemetary (there is no cemetarys in planeshift by the way, this is an example) you get a skeleton and if you would by mistake raise an undead creature from the old, like what happens if I throw raise at this lich kings grave?
Then you have a Lich king, and he will probably kill you just for the fun of it.
Skeletons and Zombies have no mind of their own so if they are not commanded to do something they will just stare blankly in the air even if they are attacked.
Back to the summoning, small monsters are easy to intimidate, therefore it\'s pretty easy to make them join your side, if they are not intelligent you charm them as a part of the spell, high level monsters as a dragon must be bribed, cajoled and they are to big or smart to be charmed, all summoned creatures is intelligent and they will protect themself and their caster (if they are on his side), but if not charmed they will not make foolish things, if they don\'t have a chance they will run and creatures of the higher levels may turn on you if you give them orders that is a sure way of getting themself killed.