This article demonstrates one particular difficulty of interpreting students' use of language in science classrooms: determining whether a student's writing indicates a misconception or a misrepresentation. Students' written assignments from a case study are used to illustrate instances where multiple interpretations are possible. These examples indicate that teaching the language of school science is essential if students are to be well equipped to demonstrate their scientific knowledge. Some suggestions for facilitating the learning of the language of school science are also provided. (Contains 4 figures and 2 tables.)