This research brief from The New Teacher Project synthesizes evidence on how teacher expectations shape K–12 student outcomes and influence educational equity. The report examines how expectations are formed, how biases related to race and socioeconomic status affect teachers' beliefs and behaviors, and how those beliefs influence students' academic experiences and opportunities. It finds that lower expectations for students of color and students experiencing poverty can create self-fulfilling cycles that limit achievement through mechanisms such as fixed mindsets, weaker teacher-student relationships, and reduced access to rigorous learning opportunities. The report also highlights research demonstrating that teacher expectations can be strengthened through targeted interventions, including growth mindset practices, empathy-based approaches, and inclusive instructional strategies. It concludes with recommendations for designing comprehensive interventions that address beliefs, relationships, instructional practices, and classroom environments to promote high expectations and improve outcomes for all students.