To deactivate:

1. On the Teachers tab, select one or more teachers. (To select multiple teachers hold down the Control/Command key or the Shift key as you click to select teachers.)
2. Click the "-" button
3. In the confirmation dialog, click Yes
4. The teacher(s) will no longer appear in the list of active teachers, and won't be able to access Vizzle 

To reactivate:

1. On the Teachers tab, uncheck the Active box to view the deactivated teachers
2. Select one or more teachers
3. Click the Reactivate Teachers button
4. In the confirmation dialog, click Yes
5. The teacher(s) will no longer appear in the list of deactivated teachers, and will be able to access Vizzle