This report is a synthesis of 79 empirical research studies on assistant principals published since 2000, including both quantitative and qualitative studies. It also includes new analyses of national data and data from two states, Tennessee and Pennsylvania. This report provides a descriptive portrait of the assistant principal role. It then addresses two important issues: 

1. diversity and equity among assistant principals; 

2. assistant principals’ influence on student and school outcomes. 

The report addresses five research questions:

• How prevalent are assistant principals? Which principals tend to have experience as an assistant principal?
• What are assistant principals’ leadership roles?
• What is the pathway to the assistant principalship and from the assistant principalship to the principalship?
• How does access to the assistant principalship and principalship differ by educators’ race, ethnicity, and gender?
• What is the relationship between the assistant principal role and school outcomes? What is the relationship between experience as an assistant principal and future principal performance?