Id like to change over the summer?

Join a gym or if not, go out for runs or do workouts at home. You shouldn't really be changing just because you're going to high school though. It's not all about looks! But if you want to get more into shape and become fitter, go out for regular jogs - about three times a week. Buy some weights that you can use at home and work yourself up by increasing the size of the weights after a while. If you want to build muscle, your diet should contain lots of protein, which helps muscle growth. However, this only works when combined with regular training. Otherwise, it can just make you gain weight with no muscle girth.