This article demonstrates how literacy practices in an 11th grade, urban, English classroom in the United States worked to delineate and patrol gender borders between acceptable masculine and feminine social practices. Drawing upon Blackburn's (2005) and Thorne's (1993) studies of the gendered boundaries that are created and questioned in literacy events and classrooms, this ethnographic study explores how the students and teacher of the class actively constructed parameters of acceptable feminine and masculine social practices and policed each others' performances and representations of these practices through the classroom discourse surrounding literacy activities. I argue that heterosexuality was a primary characteristic of acceptable forms of masculinity in the class and that laughter was a primary discursive mechanism through which students marked gendered border crossings, particularly when boys' behaviour was interpreted as feminine. I also examine the social and literacy practices of those students who were successful at challenging and crossing the gendered borders that were constructed during classroom discourse. (Contains 1 footnote.)