In Schoolrunner, it's possible for some users to lock their class attendance records. This is available for class attendance only, and not daily attendance.
Any records saved by users with the "Lock Class Attendance" permission are locked in such a way that other users (who don't have the permission) cannot edit or change them. But note that if you have this permission, other people that also have the permission can change your records.
This permission is ideal for front office staff, who are often responsible for excusing/logging student absences based on conversations with parents or guardians that other staff members may not be aware of. It's also helpful for culture and attendance administrators. The general teacher population at your school should not have this permission though, since its value is diminished as more and more people have it.
When an attendance record is locked, users without this permission will see a lock icon next to records on the Class Attendance page, in the student class attendance grid, and in list views. Users without the "Locked Class Attendance" permission will be able to hover over the icon to see who locked the record.
If you have this permission, you can unlock records by deactivating them. (Remember that a deactivated attendance record equates to a student being present.) This means that all other users (regardless of whether or not they have the "Lock Class Attendance permission) will then be able to log class attendance.