This study builds on recent research that has found that teacher perceptions of parental involvement in schooling are an important influence on student outcomes, in addition to the effects of parent reports of their involvement. Using data from TIMSS 2003, this study explores the relationship between principal perceptions of parental involvement and student milieu and the impact of both on student achievement in mathematics. Moderated multiple regression analyses were used to explore these relationships. A significant relationship was found for mean school mathematics achievement regressed on principals’ perceptions of parental support and involvement at both Grades 4 and 8. However, statistically significant evidence of milieu moderating those relationships was not found. This may be because low statistical power is often associated with moderated hierarchical regression analyses. Significant interaction terms suggested that moderation may be found with more power. Further investigation into these relationships is suggested.