The authors argue that mathematics and science teachers must be culturally efficacious and engage in responsive practices to work effectively with English learners (ELs). They claim that the design of teacher preparation programs plays an integral role in the efficacy development of the teacher. The findings reveal that program and school-context experiences work in tandem to support mathematics and science teachers’ efficacy in working with ELs. The qualitative evidence indicates that these secondary mathematics and science teachers are supported through Accelerated Teacher Education Program (ATEP) to become culturally efficacious. Specifically, for mathematics and science teachers working with ELs, ATEP program sources of efficacy include the cohort model–community of practice.