1. Click on the Enrollment tab 
  2. Click on Re-enroll Families
  3. Click the check box next to the family/families you wish to re-enroll
  4. Click the blue Select A Batch Option box and select Rollover Selected from the menu
  5. Click Submit in the pop up window confirming you want to roll over the family/families
The family/families you rolled over can now be found in the Pending Families folder. 

How do I remove graduating students?
Refer to Knowledgebase article How do I remove graduating students