If you've registered in the wrong school or you've moved to another school, you can change your school settings in your profile. It's very easy! Just go to your Profile section and from there click on the "Change school" button.
Keep in mind that, for privacy reasons, to change your school will involve deleting all your classrooms and assignments.
There is a limit of one change every 6 months. Once, you have done the available change you will see a message which will inform you about the date when you will be able to change your school again.