Enable the lock mode in order to freeze the attendance after a certain set duration. When enabled, editing or marking after the allowed date can only be done by a privileged user or admin.
Step 1: Menu > Academics > Attendance > Attendance Settings
After the settings, you will get two options as 'Submit' and 'Save' in the Attendance register page as shown below,
Save - Save the attendance using this option. You can edit the attendance after entering.
Submit - If you click on Submit, the attendance will be submitted and locked.