Here's a list of individual student bloggers, grades 6-8. Their posts are about digital citizenship & science. I'm sure they would love students to comment on their blogs.
The Future City Competition is a national, project-based learning experience where students in 6th, 7th, and 8th grade imagine, design, and build cities of the future.
With this at its center, Future City is an engaging way to build students’ 21st century skills