This study examined the initial efficacy of World Generation (WorldGen), a Tier I social studies instructional approach for emergent bilingual (EB) students and their native English-speaking (non-EB) peers in Grades 6 and 7. WorldGen builds on prior research on instructional practices that have been associated with improved content knowledge and literacy outcomes for EBs in classes of students with varying English proficiency. Using a within-teacher design, middle grades world history teachers' classes were randomly assigned to WorldGen treatment (17) or comparison conditions (16) for three to four approximately two-week units. The student sample included 42% EBs. Students in the treatment condition (n = 373) scored higher, on average, on world history content (Hedges' g = 0.47) and vocabulary knowledge (Hedges' g = 0.41) than students in the comparison condition (n = 343) but no statistically significant findings were yielded regarding disciplinary literacy skills at the end of WorldGen instruction. Of primary interest, the statistically significant main effects indicated that world history content knowledge and vocabulary learning was similar for both current EB and non-EB students in the treatment condition. The findings provide initial support for the use of the WorldGen instructional practices for improving content acquisition and vocabulary in general education social studies classes with students with a range of English proficiency. Furthermore, teachers perceived the WorldGen instructional practices and materials as providing the information and learning experiences necessary to support students in meeting grade level expectations. [This paper was published in "Reading Research Quarterly."]