Hey! I’m sorry if this is a late reply, I’ve been travelling the last 3 months.
What I always try to do is pack healthy snacks. My fav is hummus and carrots. Or berries ohhhh mannn berries. Also, I’m not sure how your school works but in high school we had to carry cash to use at the canteen, so if just nip that in the bud by leaving cash at home if possible! Save some money and some unwanted cals haha it sounds like you have quite a healthy lifestyle anyways. It’s just the little steps that help ^_^