Wait how is Claude weaker if he has the purest spirit energy possible?

The decent book and plot are a bit unique but I don't really like MC personality. He is hot-headed and a bit of a wimp. Also, I do not understand some of the decisions he makes. Near the start of the book, the principal + teachers are laughing at him and making fun of him and he still wants to stay in the school. Makes no sense as there are literally no benefits to that. Would consider the story average.