Our approach to emotion in school mathematics draws on social semiotics, pedagogic discourse theory and psychoanalysis. Emotions are considered as socially organised and shaped by power relations; we portray emotion as a charge (of energy) attached to ideas or signifiers. We analyse transcripts from a small group solving problems in mathematics class, and from an individual student. The "structural phase" of analysis identifies positions available to subjects in the specific setting, using Bernstein's sociological approach to pedagogic discourse. The "textual phase" examines the use of language and other signs in interaction and describes the "positionings" taken up by particular pupils. We then focus on indicators of emotion, and find indications of excitement and anxiety, linked to participants' positionings. Finally we consider implications of our approach.