I've never been a really big fan of using journals in math class. I think my dislike stems from the fact that the few times I've tried it I always had a large percentage of students saying "I can't do this" or "I know how to do the work but I can't explain it". As a result of the students being frustrated I too became frustrated and gave up.
I recently attended a differentiated instruction session where I was reminded about math journals. This time I wanted to make them work. I decided that I would train my students to be good journal writers. I figured that on past attempts I just gave up too early. I also decided that I would use journals not only to let me know what students understood but also to let students understand what they needed to work on. I know that this sounds obvious but in the past I would hand back journals, students would look at their mark and put them in their book never to look at (or think about) them again.
This time students were to write a summary of right angle trigonometry. They needed to tell me when it was used and how to use it. I collected the the journals and graded them immediately. I handed back the work to the weaker students and withheld the work of the stronger students. The stronger students became my subject experts. I paired strong students with weak students. The strong students had to explain the concepts to the weaker students. I then posted four problems to work on. The experts were to walk the weaker students through the first problem. The rest of the problems were worked on individually, but the students could check with each other to see how things were going. The next day I had all students redo the journal article.
How did it go? I think most students seemed to enjoy the experience. They didn't enjoy the journaling at first but seemed to enjoy the collaborative approach. When students rewrote their articles there was far less complaining. I even had some students ask if we could do more of this type of work.