balance doesn't have a tower... i don't know why but it just doesn't... unless i'm missing something very obvious... meh i don't know but it looks like balance doesn't have a tower. but to be honest towers are useless, people only organize meetings in there and scam people with the "codes for cards" trick.
That's the balance school, not the balance tower. To be honest, i really don't think there is a balance tower. And btw, towers aren't useless ppl do battles there. For example, ice students have to battle a colossus in the ice tower for a quest. And I'm not sure if this is true but i think you have to battle cyrus in the myth tower when you get to dragonspyre.
Balance doesn't necessarily need it's own tower, because as you are taught when you are a Balance student, Balance is the magic that is balanced out between all of the schools. Which means that basically Balance is all of the towers. I've been a long time Balance fan, but i've never really felt the need for our school to need a tower as much as it has a dog on the side of the street and an old krokotillian in a hole in the ground. :-)
And as TotalAwesomeness said, people do fights and such in their towers, and Balance at one point has you fight the three of bosses of the Storm, Ice, and Fire towers. (which can be taken as we can take out more enemies fast then the three [just an opinion] )