Text-message programs are increasingly popular as low-cost interventions aimed at improving a variety of health and education outcomes. This study analyzes participant opt out decisions from a set of text messaging programs aimed at fostering parent–child interactions and improving school readiness. Exploiting random assignment of parents of young children to programs and rich data on text messages and recipients, we examine how program design and text and recipient characteristics predict program opt out. The results provide evidence that the text messaging programs reach the parents of traditionally less-resourced children and show that program design affects parent opt out. Programs that provide context and encouragement along with activities reduce opt out compared to programs that send activities alone. A high quantity of texts and more complex texts lead recipients to opt out at greater rates.