change Guest User login name

I want to know IF and HOW to change the login screen name of the Guest User account. i want the Guest User account to show "Physics Student" at the login screen.

I am running 10.7.5 on 2010 iMacs

I am setting up a computer lab for my school.

for years now, i have been trying to lock down most OS X features such that the students can't change vital settings and thus causing issues for the students who come in later that day.

I have used the Simple Finder with Parental Controls and it has worked OK

However, i have found that by using the Guest User account w/ the Simple Finder and Parental Controls will give me the desired protection that i want.

Today, i have figured out how to customize the Guest User account with particular System Settings and App settings such that when you logout and log back in you get a clean start w/ my specific system settings.(background, application list, application toolbar settings, etc)

To that, I also figured out how to change the login screen image of the Guest User to anything i want (it was a simple change)

Unfortunately, to complete my customization of my Guest User account, i would like to rename the accounts login name (not the official OSs' account name)

Does anyone know how to do this?

please advise

please and thank you