Recent studies have shown that texting-based interventions can produce educational benefits in children across a range of ages. These studies vary in their focus from broad curricula on child development, to reminders about missing work, to steps needed in order to enroll in college. Given the potential effectiveness of texting, as well as the ease of systematically varying texting programs so as to assess the effects of different approaches, texting provides a productive venue for learning about mechanisms behind program effects. This study tests the effects of a text-based parenting program for parents of kindergarteners, distinguishing the effects of a general program for all children from a program that adds differentiation and personalization based on the child’s developmental level. We find that the personalized and differentiated program is more effective than the general program and that these benefits are driven by the gains of children further from the average learning levels of development. Overall, children in the differentiated and personalized program were 50 percent more likely to be reading at a higher level (p<0.01) and their parents more often reported that building their child’s reading skills is easy by 0.44 standard deviations (p<0.01) than children in the standard program. In addition, parents who received differentiated and personalized text messages reported engaging more in literacy activities by 0.31 standard deviations (p<0.01) when compared to parents in the control group. Differentiation and personalization, however, may have caused parents to interact with their child’s teacher to a lesser extent, perhaps due to receiving information from another source.