Dear Mike,
Good day!!
As per the description shared, I understand your concern and I would like to convey that I have tested the behavior at my end, where removing the attachments added to the assignment will not remove the attachments from the students view.
Since the attachments added to the assignments in the Class Team will be stored in the SharePoint Online site associated with the Class Team. So, I have tried deleting the attached files from the SharePoint Online site as well but still the deleted attached files are showing in the students view.
So, I request you to delete the assignment and create a new assignment with the required attachments, so that the students will only work on the attachments which are necessary.
I agree with you on having the ability of removing the attachments for the students when teacher removed the attachments in the Class Team on Microsoft Teams will benefit the users and I suggest you to add your valuable idea as feedback in the Microsoft Teams · Community which is the best place to share our ideas and improve the Microsoft products.
Appreciate your patience and understanding. Have a great day!!
Best Regards,
Sophia