Just when we expect them to be more mature, teens turn to rebellion as their way to express themselves. Actually, I believe that it's more of a psychological phase when we make excuses for their developing bodies, identity, and freaky personality. We also had our depressive, rebellious times and it doesn't matter if it's back in the 70's. It's all the same, and we just have to keep an open mind. But as soon as things get out of hand, don't you wait until your boy ends up in jail or your daughter bloats up with a baby. Violence, aggression, and anger can be a manifestation of emotional disturbance. Deal with it, but don't overreact the way any normal parent would.
