As an admin, you can invite colleagues to your account through your account settings.
Here's how:
Go to your Account Settings in the top right-hand corner of your account.
Click 'Invite Teachers'.
Add the name and email address of the teacher you want to add to your account and click "Email invitation now...".
If the teacher requires admin privileges, please select the admin role. This will allow them to view progress reports on all classes and other admin features.
Once the teacher has activated their account, they will be able to view all classes and add themselves as a teacher in the relevant classes.
