If you are trying to add a student's email address to their existing account in Seesaw, but are receiving an 'email address already in use' error, it is likely that the email address is connected to an existing student account outside of your School Dashboard.
This is common when students create an account for a class on the free version of Seesaw and that class is later deleted. The student account still exists, but the email address cannot be assigned to a new account in your school.
Please contact School Support with the name of the student, and the email address you'd like them to use. We can find the existing account and delete it so the student's email address can be assigned to the actual student account in your school.