Background: The benefits of delaying school start times for secondary students are well-established. However, no previous study has considered how changing school start times impacts sleep and daytime functioning for K-12 teachers. Methods: Teachers in a large suburban school district completed 3 annual surveys (pre-change n = 1687, post-change n = 1857, follow-up n = 1812) assessing sleep and daytime functioning. Results: With delayed start times, high school teachers had later rise times (high school [HS]: 28 minutes, middle school [MS]: 14 minutes), increased sleep duration (HS: 22 minutes, MS: 13 minutes), and improved daytime functioning. Improvements for middle school teachers were noted but were not statistically significant. With earlier start times, elementary teachers reported earlier bedtimes (9 minutes) and wake times (9 minutes), with no changes in sleep duration or daytime functioning. Implications for School Health Policy, Practice, and Equity: Today's school health policies often focus on wellness. Findings from this study reveal that the policy of healthy school start times can have a significant, positive impact on adults who teach in later-starting secondary schools. Later school start times for secondary teachers provide greater parity with their elementary colleagues in terms of sleep opportunity. Conclusions: This study extends previous findings on how the policy of later secondary school start times improves the health and well-being of adolescents, highlighting that healthy start times contribute to increased sleep opportunity for MS and HS teachers and improved daytime functioning for HS teachers, with changed start times having no significant negative effect on elementary school teachers.