Reading comprehension instruction may be critical for students to learn from social studies text, particularly for students who are not yet proficient in reading. Understanding factors that correspond to high levels of student engagement during text-based social studies instruction appears particularly important. Data were collected from 50 fifth-grade classrooms during text-based social studies instruction to explore the extent to which reading comprehension instruction, text readability, and student reading achievement related to student engagement. Data collection included a variety of methods -- observation, readability formula calculations, testing, and student ratings. Multi-level modeling was applied to examine the relationship between student -- and classroom-level predictors and student engagement. Among the predictors, only student reading achievement was found to directly relate to student engagement. However, an interaction effect was identified whereby reading comprehension instruction was found to moderate the relationship between text readability and student engagement. These results indicate a need to consider text readability level when determining the level of comprehension instructional support to provide. Additional implications for future research and practice are offered.