Letters by Computer Name
If multiple computers shall get the same configuration but act different, then the Computer Name can be used as criteria.
; USB drive on the teacher's computer on X, Y
[DriveLetters]
ComputerName=TeachersComputer
ComputerName=AssistantsComputer
Letters=X,Y
;no USB drives for all other computers
[DriveLetters]
DriveType=ANY
Letter=-
DriveType=ANY is required to block USB floppy and CD drives too.