What can I eat to stay ful lfor 5 hrs????

At school theirs long hours until lunch and my stomach roars like a sonic boom!! I've tried oatmeal but its not long enough along with fruit etc. Or what can i do to prevent that loud sounds?? Would losing weight help at all cuz I'm 5'5 129lb and 13. Kinda big lol but ya I go to the gym everyday 2 hrs anyway.