Discussing the efficiency of blogging i a pedagogic setting

What are the efficiency of blogging in pedagogic settings?

I'm working on a project where I'm trying to show how to use blogs within different settings (pedagogic settings), and for different target groups. I'm searching to find some ideas on how to efficient take benefit of blogs within these different settings and for different target groups...

How do you think one could utilize blogging for pupils in lower grade schools?
How do you think one could utilize blogging for students in higher grade schools / education?
How do you think one could utilize blogging for teachers in lower and higher grade education?
Etc....

I will within the next few weeks try ot summarize my thought within this field.