DESPITE THE RAPID RACIAL DIVERSIFICATION OF STUDENTS AND DECADES OF EVIDENCE DEMONSTRATING THE NEED FOR TEACHERS OF COLOR, THE TEACHING WORKFORCE REMAINS PREDOMINANTLY WHITE AND SEGREGATED. WHILE VARIOUS POLICIES AND LINES OF RESEARCH HAVE WORKED TO DIRECTLY STRENGTHEN THE PIPELINE FOR TEACHERS OF COLOR OR ESTABLISH THE DIRECT EFFECTS OF A DIVERSE TEACHER WORKFORCE ON STUDENT OUTCOMES, LITTLE ATTENTION HAS BEEN PAID TO THE INDIRECT BENEFITS OF TEACHER WORKFORCE DIVERSITY. IN THIS DISSERTATION, I USE PANEL DATA THAT SPANS THE 2010-11 THROUGH 2015-16 ACADEMIC YEARS FROM PENNSYLVANIA TO DESCRIBE THE DEGREE THAT TEACHERS ARE EITHER RACIALLY SEGREGATED OR ISOLATED ACROSS SCHOOLS. THEN, I ESTIMATE THE EFFECTS OF RACIAL ISOLATION AND SEGREGATION ON TEACHER MOBILITY AND EFFECTIVENESS. DESCRIPTIVELY, I FIND THAT TEACHERS ARE RACIALLY SEGREGATED ACROSS SCHOOLS WITHIN A DISTRICT. MOREOVER, WHEN WHITE AND BLACK TEACHERS LEAVE A SCHOOL, THEY MOVE TO SCHOOLS WITH 1 TO 3 PERCENTAGE POINTS HIGHER PROPORTION OF SAME-RACE PEERS, RELATIVE TO OVERALL DISTRICT DEMOGRAPHICS. IN ADDITION TO THESE DESCRIPTIVE RESULTS, I ALSO FIND THAT BLACK TEACHERS BENEFIT FROM HAVING A HIGHER PROPORTION OF SAME-RACE COLLEAGUES. SPECIFICALLY, I ESTIMATE THAT A 10-PERCENTAGE POINT INCREASE IN THE PROPORTION OF BLACK TEACHER COLLEAGUES REDUCES THEIR LIKELIHOOD OF MOBILITY BY 1.3 TO 2.4 PERCENTAGE POINTS AND INCREASES THEIR EFFECTIVENESS IN MATH AND ELA WITH BLACK STUDENTS BY 0.01 STANDARD DEVIATIONS. THESE RESULTS FURTHER DEMONSTRATE THE NEED TO STRENGTHEN THE TEACHER PIPELINE FOR NON-WHITE TEACHERS AND TO PROVIDE ADDITIONAL SUPPORT TO TEACHERS IN CHALLENGING SCHOOL ENVIRONMENTS. PARTICULARLY, MY RESULTS SUGGEST THAT TOKEN DIVERSITY EFFORTS MAY EXACERBATE, RATHER THAN ALLEVIATE, RETENTION FOR TEACHERS OF COLOR.