The default username for both staff and students is the numeric (up to 10 digits) state UID. However, we have also implemented an enhancement to allow PSUs to opt-in to using an "Alias ID". This can be the user's email address (staff and/or students), or if the PSU provides a nightly file upload, a "local ID", usually the local username used in Active Directory or another directory.
LEA Administrators interested in using an Alias ID to login should check out the Alias ID page under Resources. (It's also linked above).