Candy Series G28 - The Hero's Quest: Self-Improvement by Kaoru/Candy Factory

So he can stay friends with Mia, Cero (real name: Charles) is doing his best to become a better student. But a gang of of bad kids keeps getting him into trouble! They even lie to Mia about being good friends with Cero! How will poor Cero figure out how to do better in school and make the gang leave him alone?