GMM usernames and passwords must be unique and are case sensitive.
If a student receives a message that a username is taken, the student may already have GMM credentials. If so, the teacher should use SEARCH FOR STUDENT to add the student to the class.
If a teacher uses SEARCH FOR STUDENT and receives a duplicate student warning, pay heed to the warning.
SEARCH FOR STUDENT is a button that allows a teacher to add students (with GMM credentials) from their district to a class.
