Avoid choosing clothes that are too tight or too loose. Also avoid clothes with tears and stains. Try to choose clothes that express your personality. Follow your school’s dress code. Generally, this means that revealing or suggestive clothing is prohibited. If your school requires a uniform, make sure to wear that.
If you pack your lunch, try putting your lunch in your lunch bag and then in the refrigerator if necessary. If you prefer to buy lunch, make sure you have your lunch money. Make sure you have all of the essentials (your pens, pencils, erasers, folders, planners, etc. ) packed. Avoid unnecessary items, as they can just become unnecessary weight.
You could also take them into the bathroom with you so that you can change right there, as opposed to going back and forth between the bathroom and your room.
Make sure to wear a clean pair of socks every day.
As a last resort, you can just grab a granola or cereal bar.