In your dashboard, under ‘Options/Reading’, you need to check that the number of posts under ‘Syndication feeds’ is set to At LEAST the number of posts in your blog, and that the feed is set to ‘Full text’ before saving it as an .xml file.(look for the xml link in browser bar or meta somewhere in your theme header/sidebar/footer)
In your new blog at “wordpress.com” or “edublogs.org” for example simply import the .xml file and you are back in business.
Sadly, once you are no longer a student at St. Jerome’s your blog is gone. (Usually I don’t get around to cleaning things up until the fall, though).