This study tested the relationship between Principal Support of Teacher Psychological Needs (PSTPN) and a need-supportive instructional climate. Evidence on social contagion was used to advance three hypotheses: "PSTP is associated with school differences in student reported autonomy-support, competence-support, and relational-support; A climate of teacher psychological safety mediates the relationship between PSTPN and student reported autonomy-support, competence-support, and relational-support; A climate of organizational commitment mediates the relationship between PSTPN and student reported autonomy-support, competence-support, and relational-support." Hypotheses were tested in a sample of teachers and students from 93 urban schools in a southwestern state of the US.