Figure out if you are lactose intolerant and don’t have any milk or dairy products before going to school or during the day … have the cheese at the end of the school day.
Exercise and walk lots … not intensive just keep moving. The digestive system works better when the body is moving … the muscle movement especially your abdomen literally pumps and drives the digestive system.
The longer and more often you sit still, the more likely all that content will just sit and take longer to pass. The longer it sits, the more likely you’ll build up gas, more gas, more farting.