Blogs are a useful teaching tool for improving student writing and increasing class interaction. However, most studies have looked at individual blogs rather than blogs maintained by a whole class. We introduced assignments involving participation in class blogs to four science communication classes with enrolments of between 15 and 36 students. We administered paper-based surveys to obtain student perceptions of the value of the blogging assignment. Based on feedback in semester one, we increased commenting requirements and spent more time integrating the blog with coursework in semester two. In semester two, students had significantly improved perceptions of the blog assignments. The most commonly cited benefit by students in both semesters was that the blog helped to improve their writing. Most enjoyed the opportunity to have increased intellectual exchange with other students and the majority agreed that knowing other students read the blog motivated them to write better. Students disliked being forced to comment and they felt that they benefited just from reading other students' posts. However, we recommend that weekly commenting should be mandatory, as this increased involvement and perceived value of the assignment.