Promoting Writing in a Social Studies Class

I am wondering how I, as a social studies teacher, can promote writing in a way that is both technically sound and clear in expressing content. One thing that I do (an idea I “stole” from my classroom mentor) is to use journals as the “hook.” For many classes, students will spend 10-15 minutes journaling in a free-write manner. They are then expected to go home and expound upon their entry based on the lesson that followed the journal entry. The question students address is often either a contemporary question, a point that is very theoretical and requires no background content knowledge, or something that the student brought up. There is a standard rubric which has presentation(i.e. writing skills) as one of the five categories, but it also includes process, application, knowledge, and design (expression of thought) (the standard rubric, which depending on the unit/lesson, has different categorical assessments. I think 

I think that journals are a great way to get students to write, but I'm wondering if I can and should be doing more. I've included writing elements for every project. I'm also trying to make myself assessable to students to review writing assignments. These things are a start; I am wondering how I can continue to push writing among my students. Any suggestions would be appreciated.