Vocabulary is a building block of understanding, especially in science classrooms where language abilities are mixed. To reduce academic inequalities, approaches to vocabulary instruction need to demonstrate benefits for students across learning contexts. We summarize the results from the first unit, "Earth Systems and Catastrophic Events," in a longitudinal study investigating the effectiveness of the "Science Vocabulary Support" (SVS) program originally designed for sheltered classrooms. Four grade 7 classrooms, including 106 students (25% native English speakers; 29% former English learners [ELs]; 46% current ELs), participated in this quasi-experimental, matched-group study. Results indicated that students in SVS classrooms outperformed those experiencing regular instruction on science and targeted academic vocabulary, as well as on reading comprehension measures. We detected no significant program impact differences between current EL and proficient English-speaking students across measures. Results suggest that programs such as SVS may help teachers meet the needs of all students in mixed-English-proficiency classrooms.