When self sign-up is enabled for a group, instructors are unable to prevent students from switching groups. However, as an instructor, you can turn off the self sign-up at any time. By turning off the self sign-up, you prevent students from switching groups.
Open Group Set
Click the Settings icon , then click the View User Groups link . Or click an existing group set .
Turn Off Self Sign-up
Deselect the Allow self sign-up checkbox to turn off the self sign-up . Click the Save button .