In this article we used an orienting framework of interactional ethnography to make visible classrooms acting as cultures. We examined the interactional patterns from two different classrooms as participants jointly negotiated and constructed meaning. We first demonstrated how participants began to construct a classroom culture in the first weeks of school. Next, we examined how taking up an ethnographic perspective assisted a teacher candidate to successfully enter an ongoing classroom culture. In the last analytic sequence, we followed the discursive practices surrounding a fifth grade student who re-entered an ongoing classroom culture after an absence of four months. The results showed that using ethnographic skills of observation and interpretation assisted both the teacher candidate and the returning student to become communicatively and culturally competent members, by recognising the social and academic patterned practices that were already taking shape through the classroom interactions.