Eat Small Portions Every 2-3 Hours, But What?

Ok, so I have heard eating small portions every 2-3 hours helps you lose weight instead of not eating for long periods of time. I go to school therefore its very hard for me to diet because there is nothing healthy I can eat & also the times etc mean I cant excercise in the morning. I want to lose weight fast, I have been trying to diet for ages and give up due to not seeing results fast enough, but this time I am so determined to do whatever it takes as I am sick of my fat body! There is one healthier option which I could eat for lunch at school but I'm not sure! Its a small baguette around 15 cm filled with chicken tikka, which is just chicken ins ome sauce. Would I be able to eat this for lunch at school for 5 days a week? Other than that I would just need to eat a bit of fruit which does not satisfy my hunger and also means I will not be getting enough calories to lose weight. What should I do at the gym also? Thanks very much to anyone who answers & gives me help.