Congrats to you for deciding to do something and change yourself for the better
Do you live with your parents? Do they support you in trying to lose the weight? Have you tried talking to them about only buying healthy foods when you go shopping?
I think you should just do the 'regular' thing - eat healthily, and exercise regularly. Try just going for a walk around the block or the backyard as soon as you get home from school for 20 minutes or so, and try to cut down on portion sizes. Remember you can still eat things like chocolate or something, but everything in moderation and small amounts. I found the best thing for me when I crave chocolates or sweet foods, was to buy Jarrah hot chocolates and have one every time I felt like something sweet - they're only 40 calories each!
If you want to count calories, there's a great website that's free to join up to: http://www.calorieking.com.au
. It'll help track your exercise, calories, and your weight loss
Take it slow at first, and introduce yourself to new things one at a time to make these healthy things into habits.
Good luck hun! We're all here if you need us