In my opinion balance, its the most natural school. Nor strong nor weak, you have to focus (shield, ward) to success.
Most of us are like that. Few people are born naturally strong, most have average skills and need to support themselves with patience (aka buffs) to keep going.
My natural school is Life. I love nature and beautiful scenery views and giving a helping hand. If i would take a school test every time I create a new wizard. It would be Life.