This study assesses the effects of two text-messaging programs for parents that aim to support the development of math skills in prekindergarten students. One program focuses purely on math, while the other takes an identical approach but focuses on a combination of math, literacy, and social-emotional skills. We find no evidence that the math-only program benefits children's development. However, the combination program shows greater promise, particularly for girls. Quantile regressions indicate that the effects are concentrated in the lower half of the outcome distribution. Results imply that girls may have started the year behind boys in math and caught up to and even surpassed boys when their parents have access to the program that combines topics. Our results also provide evidence that the structure of behavioral interventions can affect who benefits from the program, sometimes in unexpected ways, to produce meaningful differences in outcomes. We discuss and provide evidence for various hypotheses that could explain these differences. (author abstract)