End of Year Cleanup/deletion


I want to remove all my students associations to start again fresh next year.
In the association screen there is a minus button and a group selection dropdown but Because all our students are network users they don’t appear to be in any group. choosing any group seems to have no effect
How does one actually delete associations in bulk.
prefer not to delete all as teachers mac laptops need an association for classwize and they don’t autogenerate.