From your portal homepage, go to User Management and and select Parents from the Parents pull-down menu to see a list of all parent accounts.
Click the name of any parent in the list to edit that account. On the edit account page, click the Disapprove link in the Approval Status section as pictured below.
Remove Parent Access To Students
The students approved for a parent's account appear at the bottom right of the account edit page. You may remove a student by clicking the "Remove student from parent account" link. Similarly, you can remove a parent from a student's account.