Catholic social teaching affirms the primary role of parents in their children's education, as well as the importance of forging a positive home-school partnership. The purpose of this article is to provide empirical evidence for further cultivating a collaborative, home-school relationship aimed at improving the mathematics performance of Catholic school first grade students by training parents as providers of at-home numeracy support. The participants included 60 parents (29 Black; 2 Asian; 1 Latino; 26 White; and 2 other) from two urban, Catholic schools. Parents randomly assigned to the experimental group received numeracy training and materials and, then, implemented a 15-week home numeracy intervention. Results revealed that students in the treatment group (or those who received the parent-child home numeracy intervention) made large and statistically significant gains in their mathematics achievement, measured by a standardized test, as compared to the control group.