MoparDJCJ

Proceed with a periodical invasion of his locker with the excuse of protecting the democracy and local stability. At the same time, you should try getting some of the dirty business of this guy and threaten him with releasing them. This way, he won't dare to tell you to stop or ask for the help of other organisms, such as the principal or parents, so once you've conquested back the space this guy initially stole you, you can go ahead with your expansionist plans and get both lockers for you.