You can use the same Classtag profile to join another School if you need to. Just make sure that you disconnect from the previous School you are connected to and join the new school.
Please follow the steps below on how to Resign from a School on Classtag.
1. Click the Hamburger menu.
2. Go to Account Settings.
3. Click Schools & Classes.
4. Click the ellipses next to the School's name.
5. Click Resign as a Teacher.