Do you still need a local file-server on your school network?
If school-owned shared computers are being used by staff and students only to access their personal files or shared resources on remote cloud servers (such as Google Drive), there is little need to have individual local network logons, or roaming profiles, etc.
So long as the computer has a network connection, it can be setup with a generic image, with a common auto-logon for everyone who uses it. Authentication isn’t required until each user connects to their remote server account – and that is managed by the cloud provider, not the school.