We describe an instructional intervention designed to help teachers engage English learner (EL) students in mathematical problem solving and learn the mathematics register. The "Discursive Assessment Protocol" (DAP) integrates Pólya's classic problem solving framework with research-based instructional strategies that benefit EL students. The research-based instructional strategies are grounded in theories of academic language development. A sample problem-solving episode is provided that demonstrates how an EL student wrote a "multiplication story" involving fractions and what we learned from using the DAP to support him and other EL students develop the mathematics register in English. Among the implications of this study is the value of selecting tasks that are not only worthwhile mathematically, but worthwhile in that they have potential to develop students' mathematics register. [For the complete proceedings, see ED629884.]