NEWBIE: Backup mail files; School

Hi everyone,

        I would like to keep a folder of backup mail for all students, identical
to var/spool/mail but in another secure location.(on same server with
limited permissions, etc.) Mail still is delivered to /var/spool/mail as well.

Is there any way to easily filter this by group membership of users. (ie
Grade 7, Grade 8, etc.)

Thanks for any assistance or pointers to instructions.

Les Richardson
H. Hardcastle School
Edam, SK, Canada