I need urgent dieting help?!?

Alright, I'm currently doing my GC-SE practice, i have so much homework that i literally don't have time to exercise. On my lunch break, i just have time to stuff a small packet of nuts or crisps in my mouth before i have to go back to lessons, we have a really short lunchtime(and i've asked, there's nothing that can be done about it) then i come home, have one meal, of around 500 calories, then a snack at bed time if i get a chance, about 100 calories, i'm 14 and i weigh 9 and a half stone, i know about body fat storage because of starvation mode, but i want to be 8 and a half stone, is there any way i can achieve this with my hectic life style? Please help me, i need to lose some weight because i feel awful when i look in the mirror, i know that Yahoo answers isn't exactly the best place to ask this but if anyone knows any weight loss methods or anything let me know. Also, how can i bring my body out of starvation mode without it storing any fat? If i eat less when come home will it help? 10 points!