You have a lot going for you, and some good solid habits! It is great that you are not a junk food lover or a soda drinker. You get a healthy amount of exercise, esp if you walk both ways to and from school. Also, good water drinking! That is a really good start.
Your main problem is your meal sizes, including skipping. If you eat a tiny breakfast and skip lunch, it is no wonder you are eating a lot after school. In order to get control, you can’t allow yourself to get that hungry. What you want to do is shift your eating more toward the morning. Eat small amounts often…maybe even once every 1-2 hours.
So in the breakfast it is okay to grab a small snack, always healthy. Don’t skip! You can fold over a piece of bread with peanut butter or cheese or something. You can also pour some cereal in a baggie or tupperware and eat it dry while you walk. Another really easy thing to do is…pop some yogurt cups in the freezer. You can squeeze the cup little by little while you walk to school and this way you won’t even need a spoon. Many yogurts are under 100 calories. Add a piece of fruit like a banana or an apple or a handful of grapes or berries, or an all fruit juice box…and you are good to go! These things can also be used for lunches.
You must make time for lunch. Bring or buy but do not skip…Healthy choices: pouch of tuna fish, add some low fat mayo at school and eat with crackers, carton of plain white milk (1% or 2%) and a piece of fruit or some baby veggies or a salad with spray dressing. All this is about 400 calories. That is a good meal, easy. Do not eat the fast food choice at lunch cafeteria. Make healthy choices at the salad bar or sandwich line.
If you are allowed to snack in class, and also on the way home, choose something easy like raisins, peanuts (if you can, sometimes other kids have allergies to peanuts) or maybe a cheese stick or a few pretzels or wheat thins. These are little tiny tiny snacks…100 calories and healthy. Try one mid-morning, and one mid-afternoon. So your school day shapes up to be breakfast on the go…2 classes…snack…2 classes….lunch…2 classes…snack…2 classes…walk and snack on the way home. See if that gets you to dinner but don’t let yourself get hungry. If not have a tiny glass of milk or a couple crackers or something.
Dinner you may not be in charge of, but keep it light, small meal, and nutritionally good. Get your parents to help you when they cook…steamed and baked instead of fried and heavy. At night you should have small servings of things like pasta. If you want these kinds of foods eat them for lunch. Also…dessert is not smart on top of a meal. But you can have some after a while, when you want another snack…maybe a half portion of something wholesome, that is….real food with some healthy ingredients like ice cream which is a lovely dessert if you don’t overdo!
For your evening snack (not another meal), choose something like a sugar free pudding or jello or a serving of yogurt, a piece of fruit, a couple handfuls of popcorn, a piece of toast with fruit spread, a cup of sugar free hot chocolate.