Thanks for the instructions to the Blojsom Admin tools. You can turn off comments, trackbacks, and even set up comment moderation etc.
As far as creating thousands of blogs, you might want to have a staff member keep track of blog usernames and passwords to start with so you or your staff can perform the admin tasks like cleaning up trackbacks and comments etc.
You should also look to Moodle, another open source material. Teachers can actually use this to put their entire course content (watch out for copyright violations!!) online for their classes along with discussion themes etc.
Reminds me of my BBS days and WildCat Software!!! (just shows my age as well)
Thanks again