<p>Cultural and linguistic diversity has the potential to enrich classrooms worldwide. Yet, research suggests teachers feel ill equipped to meet the needs of their CLD learners and links class CLD to poorer peer relations. Integrating the job demands-resources and self-determination theories, this longitudinal study used cross-lagged multilevel structural equation modeling to examine relations among class CLD, teacher self-efficacy in maintaining discipline, classroom social climate, and reading comprehension from 1st to 3rd grade. Data were drawn from 146 teachers and 2815 students (2017–2019). Results indicated greater variation within than between classrooms for both classroom social climate and reading comprehension, though small but meaningful between-class differences remained. Higher class CLD was associated with slightly less positive classroom social climate over time, while teacher self-efficacy in maintaining discipline predicted higher class-average reading comprehension at the end of second grade. No reciprocal effects between teacher self-efficacy and classroom social climate were observed. These findings underscore the importance of supporting teacher self-efficacy and fostering peer cohesion in CLD classrooms and highlight directions for future research on classroom social climate at the elementary level.</p>