Writing Responses to Open-Ended Questions
Review the Rubric with Students
Most teachers use rubrics to score student responses to open-ended questions.  Make sure students understand the rubric so that they know exactly what they must provide to get the best score. Teachers use a variety of strategies to provide this training:
Student Scoring: Save student responses from previous years. Show a sample response on the overhead (without student name) and ask small groups to decide what score the response would get and why.  Lead a discussion about what is missing from the response and have students suggest what might be added to get the highest score.
Peer Editing: Pair students to read each other's response, assign a rubric score and make suggestions or comments.

Write-On Bulletin Board: Regularly display student work that exemplifies the best response to open-ended questions.  Try to include different strategies for organizing information (table, graph, list, drawing, factor tree, etc.) so that students consistently see proof that there are MANY right ways to respond.
Use the Writing Process Approach
Students are accustomed to editing their first drafts in language arts, reworking their writing to craft a better response.  Regularly include these practices in math class.  After writing, students should use the rubric to examine their response and annotate, clarify or reorganize, as needed, to craft a tight response.  Students should be encouraged to use words, pictures and/or numbers to capture their thinking process in these open-ended questions.  They must also understand that there are many different ways to achieve a perfect score as long as they accurately show their thinking toward a correct answer.
Math Portfolios: Keep folders of students' open-ended problem solving with first draft, revised draft and annotated rubric attached.
Remember to...Checklist: Have students generate a list of things  (in their own words) that they should check before deciding their open-ended response is complete.  Add more items, based on student performance or assessed weaknesses -- e.g. label all graphs, write the unit (centimeter, inch, packages, etc.)
Math Word Wall: Encourage students to check that they have used the best math words and that they have spelled them correctly.
Writing Conferences: Conference with students to review their responses and provide detailed feedback on what they did correctly and/or how they might improve their response, as per the rubric.
Provide Independent Practice
Students will complete open-ended problems in both classroom and state testing situations, most likely under timed conditions.  Teachers should continue to use a combination of the writing process approach (to grow better math writers) and the independent response situation, in which students must apply good practices to producing their best responses under test conditions.  A combination of these approaches, used throughout the school year, is the best instruction an