To make sense of the complex information taught in the upper elementary grades -- and to understand the language that increasingly appears in high-stakes tests--students must be proficient in academic English. English language learners are at a serious disadvantage. Two word problems in mathematics illustrate the difficulties that these students can encounter in instruction and in tests: synonyms, conditional constructions, prepositional phrases, and pronoun references, to name a few. Mastering academic English requires instructional activities that actively promote language development in the context of learning intellectually challenging content. Project Challenge, a math program in Massachusetts funded by a grant from the U.S. Department of Education, provided those activities. State test results showed that English language learners who participated in the program outperformed students from many high-performing districts in the state. School leaders can help improve the poor performance of English language learners by recognizing the role that academic English plays in test performance and classroom learning and by encouraging and providing opportunities for all teachers to participate in professional development activities that address this issue. (Contains 1 Figure.)