user needs to register on another user’s blog

Here is my setup:

Latest version of WPMU installed
Teachers and students at my school all have a user account with a blog.

issue:
One teacher has a blog for each class and wants each student to be an author on the blog that corresponds to the class they attend. Instead of the teacher adding each of their 150 students to the correct blog, we want the student to be able to register themselves as an author on the teacher’s class blog (MAJOR time saver)…I added the 1267014645_mp-blog-register.php plugin thinking that it would let people register, but when a student is logged into their own blog account, the meta links only offer site admin, which of course takes them to a page that they don’t have access too (the teacher’s blog dashboard).

I have searched google, these forums, and the plugin area for something that will work, but am totally stuck. Any ideas for something that will allow a user to request access to another blog within our blog network???

Thanks in advance!