do you have a dog? take him/her for a walk for 1/2 an hour when you come home from school. (This also helps you clear your head if you've had a bad day at school :) ) Watch what you eat, that is, eat more healthier stuff. If I want a chocolate bar I take an apple, cut it into pieces and dip a bit of it into nutella (that chocolately spread stuff.) Make substitutions like that and you won't feel like you're depriving yourself, but you will be losing weight.