Having Older archives and Newer archives

I’m running a blog for a 12-week after-school program where different people running the program write about how each class went at each school.

Each post is categorized with the school name and the week #, like “Washington High, Week 3”, so you can click on the archives and see all the posts about Washington High or all the posts in Week 3.

Now that the Fall 05 semester is ending, I’d like to “archive” these posts and have a fresh clean blog for Spring 06 with new schools and a new set of weeks, but still have access to the Fall 05 posts, but maybe not from the home page?

E.g Somehow my sidebar would have a “Fall 05” link that would jump to a page that shows all the Fall 05 posts and categories, but otherwise if I’m on the main page, it shows just the Spring 06 posts and categories.

Do I need multiple different blogs, with just a hard coded link between them? Or is there some way to do this with one WP install and put all the Fall 05 posts under some different category / hierarchy structure? It feels like I need “current archives” and then “old archives”.

And of course the solution should generalize to Fall 06, etc.

The blog is at http://www.clearsighted.org/cmbi/ if that helps. As of Feb 4, 2006, you just see Fall 05, but Spring 06 is coming soon!

Stephen