How do I add teachers to all existing classes?

[RalfGesellensetter <rgx@gmx.de>]

Dear list,

to put it right: A "class" is an entire year in my system, meaning we 
have 9 classes (annual groups). Each year has their own share folder to 
interchange files (without interferring with younger kids).

Now, of course, teachers need the right to write to all of these 9 share 
folders. Initially, I just put every teacher into all annual groups by 
default. But now, year after year, there are new groups that I want 
teachers to join in. 

Rather than clicking one teacher after another in WLUS (we have 100 
teachers), I would prefer some automatism. Maybe some script accessing 
LDAP directly takeing two parameters:

# ldap_group_imply $conditionalgroup $destinationgroup

All users who are a member of $conditionalgroup (say "teachers") will be 
joined to $destinationgroup (say "year2005").

Can anybody provide such script? Or is there a better way? 

Thank you
Regards
Ralf