I would suggest making use of the Multi-Tiki feature, that is a seperate tikiwiki database for each of the courses, but you would need to code up more routines for sharing users, permissions and any other data you wish.
120 blogs isnt all that much for a system like TikiWiki. If you wanted to improve the display on listing blogs, you should add a filter to filter by course instead maybe . That would be only a couple of hours work at the very most. Then still you have a single tikiwiki installation to manage.
Hope it helps, contact me if you want more details.