Autodesk recommends unassigning students at the end of every term or beginning of the next term to free up seats for other students.
As an administrator of your Autodesk account, you have access to usage analytics in Autodesk Account, which shows the number of seats remaining by product.
For schools with SSO enabled: If you reach the seat count for a product and a student tries to sign in and there are no entitlements available, the student is redirected to the Education products page where they will be able to access and download products on their own.