Are you aware of any blog sites for high school students that would be beneficial for this type of collaborative project?
Not really clear what you're asking here. If you're asking about where to get a free blog for students, then I'd recommend WordPress.com, hands-down. This is a free blog-hosting service, without ads, and is easy to use. You're not teaching math or science, but I know some who read this are, and WordPress is the best for math & science. There are other blog-hosting sites that are just fine for non-technical disciplines such as 9th grade world studies, but I wouldn't recommend these for math or science. Blog sites in this category are Blogger (free) and Typepad (not free).
If you want students to get into wikis as well, I'd recommend Zoho wiki (also free).
If that wasn't what you meant, can you clarify?
I like that idea. I've seen others do it, some successfully and some unsuccessfully, but most don't try.
Here's a handout I put together for a session I presented a few times last year at math teacher conferences. Some of the sites listed pertain to math & science, but most can be applied to any subject.
Hi Amy -
Perhaps a couple of these posts might be helpful:
Hope they're some help. Good luck with this effort!
I would recommend checking out Tumblr, KidBlog, and Edmodo. These three sound like they might best meet your objective for collaborative and global blogging. Tumblr has an option for readers to sign in, leave a post and comment. KidBlog and Edmodo can host multiple bloggers in one central area and also has the option for readers to jump in on posts.