The purpose of this study was to explore the socio-cultural practices and interactions of learning science in a science classroom within the concept of communities of practice. Our qualitative data were collected through observing, taking field notes, and conducting interviews in a public science classroom during an entire school year. The study occurred in a seventh-grade classroom with a veteran physical science teacher, with more than 10 years teaching experience, and 22 students. For this article, we presented two classroom vignettes that reflect a sample of the participation, practice, and community that was observed in the science classroom on a daily basis. The first vignette illustrated a typical formula of InitiationResponseFeedback (I-R-F) that transfers knowledge to students through a teacher-led discussion with the entire class. The second vignette described a laboratory activity designed to allow students to apply or discover knowledge through practical experience, while taking responsibility for their learning through small-group work. The normative practices and routine behaviors of the science classroom are highlighted through the description of material resources, and different modes of participation accompanied by assigned roles and responsibilities. What we observed was that laboratory activities reproduced the epistemic authority of the I-R-F rather than creating collective cognitive responsibility where students have the independence to explore and create authentic science experiences.