Can I close the Enrollment portal completely for certain students so that families cannot access it?

Yes, it is possible to close individual students Enrollment Portal.

1. Run the Find (Re)Enrollment query on the Online Enrollment homepage to find the student whose portal you want to close.
2. Once the Student in question is pulled into your query, click on the View Detail link next to the student's name. This is their Enrollment Detail record.
3. On the General Tab, switch the "Is Portal Open" flag to "No".  The parent will now get the unavailable message that has been configured on the Enrollment or Re-Enrollment configuration screen when they try to access the portal.