This study analyzed data from the 2018 Teaching and Learning International Study of secondary education teachers to investigate differences in instructional practices of mathematics and science teachers in relation to the percentage of English learners (EL) they instruct. The study used a series of regression models to examine if EL class composition and teacher self-efficacy are significant predictors of clarity of instruction or cognitive activation practices. Further tests investigated whether the interaction of these terms moderated instructional practice. Results indicate that mathematics teachers increase the use of clarity of instruction but decrease cognitive activation practices with increased numbers of ELs but showed no correlation to instructional practices for science teachers. Results do not support a moderating effect of teacher self-efficacy on the relationship between instructional practices and the percentage of ELs in classrooms, suggesting that trends associated with class composition are independent of teacher ability beliefs.