The traditional approach to the education of language minority students separates English language development from content instruction because it is assumed that English language proficiency is a prerequisite for subject matter learning. The authors of this article take the alternate view that the integration of inquiry science and language acquisition enhances learning in both domains. The report describes a conceptual framework for science–language integration and the development of a five-level rubric to assess teachers' understanding of curricular integration. The science–language integration rubric describes the growth of teacher expertise as a continuum from a view of science and language as discreet unrelated domains to the recognition of the superordinate processes that create a synergistic relationship between inquiry science and language development. Examples from teacher interviews are used to illustrate teacher thinking at each level. © 2002 Wiley Periodicals, Inc. J Res Sci Teach 39: 664–687, 2002