Complete passages from How Things Work by connecting sentence fragments using logic of grammar and context.
Students who work through these strategies start to make the connection that "what I think" is "what I should write" and this realization, along with posted prompts, helps reluctant writers get started on written expression of important mathematical concepts or explanations of their thoughts and problem solutions.   Partner sharing and listening to classmates read their writings encourages editing and fosters the notion that math writing isn't perfect on the first draft.   Sometimes it's just important to get some thoughts down on paper, but sometimes, as in responses to open-ended assessments, students must carefully check responses against rubric requirements.   Saving writing samples in student portfolios will allow students to see their own growth over the course of the year and this practice helps students develop confidence in their ability to meet the demands of the varied writing assignments.