All scientists depend on both reading and writing to do their scientific work. It is of paramount importance to ensure that students have a relevant repertoire of practices they can employ when facing scientific content inside and outside the school context. The present study reports on students in seventh grade acting as researchers. Over an 8-week collaborative research period, students posed their own research question, attempted to answer it by systematically testing hypotheses, discussing findings, presenting their conclusions, and documenting their process in a written report. Drawing on the perspectives of New Literacy Studies--which sees literacy as socially situated--we analyze the purpose of all the 21 participating students' texts (n = 344). Video observations and interviews with students are used to contextualize the writing events. We find that the students chose to write multiple kinds of texts for a variety of purposes. Analyzing purpose and the context, three stages of socialization into scientific writing is revealed, ranging from what the students write on their own initiative, via texts written through challenges to demanding research tasks scaffolded through writing instructions given by the teacher. Further, the students emphasized the relevance of both the research experience and the writing to their future adult life.