It actually depends. Fire-Kill opponents with DoT spells, offensive school. Ice=Tank school, high health but not as big in damage. Storm=Offensive school. Bad health and accuracy like fire but is slightly worse but good for dealing large damage. Life=Healing others, high accuracy, good health, but not best with damage. Myth=Minion class, okay damage. Death=Drain health from opponents and have health come back to you, draining spells. Balance=A little bit of everything (mostly...) I know you said you already have ice, balance and death but it actually depends on what you want/like. -Jasmine FireBlade, level 86 pyromancer.
I am a Death student ( Tenure for Dworgyn! ) but I would make a Fire character. Not to bad of health, great with multiple attacks and strength. I would choose Ice as a secondary school for tower shield. Myth is another great one! It gives good attacks, even though some are disgusting, it has spells like Basilisk which leave a leaf ( tongue twister! ). I would choose either Myth or Fire.