This paper reports on research in the analysis of high school and middle school students' appropriation of the Research Article genre in science classes. The appropriation of this rhetorical form is proposed as a measure of students' understanding of adult argumentative practice in science and the effectiveness of a learning environment in supporting the development of this understanding. An important part of this research has been the development of a coding scheme to enable the comparison of genre appropriation patterns across a large number of texts from a variety of school and curricular settings. The coding scheme produces a series of numerical scores to indicate such things as students' fulfillment of the standard rhetorical moves of scientific research articles, the written personas that students project, and the ways in which they use sources and authorities to support argument. Because the analysis of genre appropriation is a relatively non-invasive way of conducting research (when compared to survey instruments, for example), this method can provide a useful tool for reformers to compare outcomes from iterations or conditions of curricular experiments aimed at developing students' understanding of adult persuasive practices in the sciences. Contains 16 references. (Author/NB)