The paper applies Goffman's frame analysis and ethnomethodology to student performance on mathematical word problems. In educational research, frame analysis has usually been limited to primary frames. Instead, in this paper I focus on the kind of secondary frame that Goffman calls 'utilitarian make-believe'. The data consist of a fragment of verbal interaction between a teacher and a 12-year-old pupil during an oral mathematics exam. By evoking the idea of 'as-ifness', word problems introduce pupils to a make-believe world. The text consists only of 'filler words' because what really matters are the figures. Word problems and possibly other aspects of schooling can be interpreted in terms of a utilitarian make-believe key. Readiness to adopt this make-believe frame when required may be the difference between school success and failure. I argue that maths achievement takes more than just 'being good with numbers'. It is a joint enterprise of people interacting within a culturally-shaped setting, organized so as to make some phenomena stand out rather than others. Finally, I argue that 'word problems and possibly other 'school genres' could be added to the list of utilitarian make-believe frames provided by Goffman.