In a fifth-grade transitional bilingual class in Hartford (Connecticut), a project was conducted to focus on writing to learn in science. The process of writing facilitates development of critical thinking, deepens understanding of science content, and develops collaborative learning skills. The example of a set of lessons on the skeleton illustrates how students write their own books about the skeleton. The book format created student interest and enhanced motivation, but experiences with this project indicate that some adjustments are needed to teach the lessons in the future. Among the problems was the limited technical vocabulary of these students who were learning English. In addition, the school lacked reference materials in English and Spanish to support student learning. Results indicate that students writing to learn in science used writing to understand the science content and then improved their writing through the projects. (Contains 11 references.) (SLD)