Light for the Necromancer.

I generally never take Light and Darkness, or Chaos and Summoning, at the same time. And if I have to choose, I usually prefer schools whose spells are always available in my home town. Although, I do make exceptions when choosing schools. But that's only on unusual maps.

I also never take more than two schools of magic. All schools have excellent spells and abilities. But you also need to level up combat skills.