This paper examines the special challenges that English-as-a-Second-Language (ESL) students face in succeeding in science classrooms in U.S. schools. Particular focus is on how students in one experimental classroom (a Grade 2 and Grade 3 two-way bilingual English-Spanish class in a small western city) learned to apprehend scientific meaning with their peers, their teachers, and the researchers through the collaborative construction of a language of instruction for successful science learning. This was done in the context of student-generated computer models. Through active participation in the construction and use of this language of instruction, students made significant strides in acquiring ways of thinking, acting, and talking that should lead to their continued success in science. Student-generated computer models, in conjunction with the construction of physical models and other hands-on activities, can provide an effective strategy for mediating the difficulties that English language learners often have with mastering the academic discourse of science. The project goals were to help students to provide better explanations of natural phenomena, to teach them to view science as process of inquiry rather than a body of facts, to encourage students to pursue their own understandings of scientific concepts as well as learn traditional academic concepts, and to explore the effects of modeling on the participation and success of both girls and language minorities. (Contains 37 references.) (KFT)