How do I unmount network shortcut on local user log-in?

[jeju]

For our music iMacs we have local log-ins with a network shortcut icon that allows students to access their shared drive. I think you know what is coming - a student (jsmith) ticked 'remember my details' when he used this shortcut so every student that now uses that mac gets straight into jsmith's shared area.

Can someone remind me how to fix this, I seem to remember successfully fixing it last year but now cannot find the documentation.

Many thanks from the man on the rock