This study examines whether board diversity, board practices, and principal influence over board decisions impact board effectiveness across independent schools in Victoria, Australia, and to what extent board effectiveness is associated with academic and financial performance of the schools. Analyses were based on survey data from board Chairs and board members within independent schools. Results show that diversity of board composition and board practices contribute to increased board effectiveness, whereas board effectiveness is less robust in schools with stronger principal influence over board-level decision making. The results provide an indication that while some board attributes (i.e., diversity of board composition and board practices) indirectly influence school performance through their positive association with board effectiveness, excessive influence of the principal over board-level decisions may impair board effectiveness.