Students learn how to write in English class, but they seem shocked when they are told that they can put those skills to work in science class too, since writing is a huge part of science to communicate ideas, results, conclusions, and opinions to other scientists. The author of this article, a middle school science teacher, describes how he uses writing in his science classes to assess student knowledge. Writing assignments allow students to present all of the information that they know, as opposed to traditional tests where they are only able to demonstrate their knowledge of specific questions. Three types of science writing assignments are described: persuasive writing, role playing, and imaginative writing. Used sparingly, this approach enables students to be more eager to complete assignments and show off their knowledge. (Contains 3 figures and 2 online resources.)