http://www3.moe.edu.sg/edumall/rd/litreview/weblogs_in_education.pdf

Weblogs in Education a paper by Tan Yuh Huann, Ow Eu Gene John, and Jeanne Marie Ho Pau Yuen. This paper has an excellent chart that lays out the benefits of blogging in education. 

They also talk about the down side of blogging: plagerism, legal liabilities,copyright,defamation,racism. All of these need to be addresses by the teacher before allows blogging into the classroom.