This paper examines how extreme heat during the school year affects teacher effectiveness and student learning, focusing on how teacher age amplifies these effects. This analysis is based on matched student-teacher administrative data with high-resolution temperature data and uses fixed-effects regressions to estimate the causal impact of heat on test scores and teacher absenteeism. Results show each extreme heat day reduces student test scores for teachers in the oldest 10%, with nearly zero effect for younger teachers. Older teachers also experience 1.5 times more absences per heat day than younger teachers, highlighting climate-related disparities in education and underscoring the need for targeted teacher support, infrastructure investment, and heat emergency protocols.