You should read the book Positive Discipline. It will open your eyes. Kids have reasons behind what we they do. They are not just acting up. They are expressing a need or a problem. Dealing with the emotion behind the behavior is the most effective way of making a long term change in the situation.
It takes time. It works over weeks rather than a matter of a few days, but it is very worth the effort. You will be looking at change on a deep level, one made from understanding rather than fear of punishment or a desire for reward.