Do kids blog?

Mitch Denny asks: I wonder what would happen if we encouraged school students to keep an open log of their thoughts about their studies that was accessible to teachers and parents where they could ask questions. Parents and teachers could then read the blog entries to help identify ways to help the student learn.

And I was wondering, what % of school kids currently blog? Has anyone seen a stat (in Pew etc) that pulls out that stat? I can think of a bunch of reasons having kids blog would be a good thing. There was lots of crapola that I went through as a kid which would have been good to communicate with someone outside of my immediate circle about.