A couple of years ago blogging was all the rage in the classroom. The idea of having our students become content creators instead of just consumers was almost impossible before blogging came along. It gives students the opportunity to feel like their opinion matters and that they can publish their opinion for anyone in the world to see.
I can see a blog being useful in middle school, high school and beyond so that students can have a place to reflect on their learning and feel safe expressing their thoughts and reflections. I have used KidBlogs several times in an upper elementary school classroom but did not have as much luck with it because of the maturity level of the students and their lack of delving deeper into their own thoughts and opinions. It would be useful in a Language Arts or Social studies classroom because those subjects allow for opinions and thoughts to be written and shared. Another way to look at a blog is not just explicitly asking a question or stating an opinion but as a sort of diary. This can be very powerful for students who need extra practice in writing.
Sometimes a teacher can be overwhelmed with reading all of his/her student blogs. In that case, they should be carefully assigned and not necessarily used for nightly homework. Another option is to insist on peer review and assessment to alleviate the pressure off of the teacher to give critical feedback.
In order to assess student blogs, carefully designed rubrics need to be created for blogs that may be different than assessments for essays or research papers. The rubric needs to be discussed at length with the students so that they know exactly what the teacher expects. Students need to understand that blogging is a form of writing and all grammar rules and punctuation need to be followed even though it can be perceived as a more relaxed method of communicating like texting.
Blogging can be a very powerful tool for both the student and th parent. and can connect your classroom to the rest of the world!
I wrote this article a while ago. It might help you on your blogging journey!
Why Teachers and Students Should Blog
http://www.edudemic.com/how-and-why-teachers-should-blog/