@crosst ...
Full disclosure... I have no experience with ClassLink, so I do not know how it works in conjunction with Canvas. Have you taken a look at this Guide?
How do I deactivate an enrollment in a course? - Instructure Community (canvaslms.com)
You may need to speak with your school's Canvas administrator about this to see if deactivating students from your course roster would be a better alternative than completely dropping them from the courses. Pay special attention to the information in the light blue box at the top of that Guide.
I am not sure if this will help at all, but I thought I'd provide you this information just in case. Good luck, and keep Community members updated on your progress.