Massive User Creation
The Massive user creation-tool, is a plugin that lets you create a bunch of users at once. You can prefix usernames (e.g. cl123 if its a course-users for 'class 123')

What you propably need in addition to this tool, is a script that makes homedirectories based on info from LDAP - or make use of pam_mkhomedir, so homedirectories will be automatically created at first login.

Feel free to ask - we don't bite :-)