The student login uses a loginhook script to copy a student directory into the current student directory. This keeps everything clean when the student logs in.
The challenge is to keep the student directory small so that the copy time is not too long.
Studio 5 had about a fifteen minute login wait. It should only be about a minute. A careful Terminal search revealed a huge amount (about 14GB) of files in the .Trash folder. RM -R .Trash solved the problem.