Charming main male character

The main male character is charming. He is handsome and laid-back. He always wears sweatpants, but to be honest, his outfit looks really good. Of course, he looks better in suits. The first season tells his revenge on his nemesis, while the following two seasons don't have a main storyline. The classroom atmosphere is easy to immerse in. The characters are way too extreme. Some of the behaviors don't make sense, especially the revenge and the other weird kids. There isn't a single normal kid. Each episode always begins in drama but ends in a lesson or a moving way. I dislike the change of actors without notice in the beginning of Season 2.