Your interviewer is getting a good indication of your verbal communication skills during your interview process. But because written communication skills are so important in the success of a Curriculum Developer, your interviewer is posing this question to you to get an idea of your strengths as a writer. As you rate your written communication skills, be sure to talk about your written projects from previous roles. Don't hesitate to talk about formal curriculum instructions you have written. Even discussing clear and consistent communications in email and memos is important in this role as well, so talk about why taking the time to write clearly is important in your work. However you answer, make sure that your interviewer walks away knowing that written communications are essential to your work.