You should read in your free time and sleep more in the night.
Your bed time should be around 9 PM.
You had better take a tasty breakfast every morning, before school time.
You should play computer games just in weekends.
You have better go in park for jogging or join a football team, then playing computer games.
You shouldn't be afraid of getting bad marks if you will have a daily healthy program and in this way you shouldn't be worry about making your parents unhappy.