Aggressive behavior usually has some sort of motivation behind it. For younger kids, especially, it's because they are not able to verbally communicate what they are experiencing. Even for teenagers, I think toddlers and teenagers are the same type of being in a different size body. That disconnect for them is really difficult for them to figure out what is going on. If you can ask them questions, for older kids, they can come up with an answer. Ask them why they are feeling aggressive and you might be surprised at what comes out.