We evaluated the cost-effectiveness of instructional coaching and parent coaching models in Head Start using a randomized trial. The study design allowed us to compare the individual effects of each coaching model as well as their combined effect on student outcomes. Teachers receiving instructional coaching improved their use of language and literacy instructional practices, while parents receiving family coaching showed increases in numerous responsive parenting behaviors associated with positive child outcomes. Instructional coaching was more cost-effective than parent coaching in promoting these evidence-based practices. However, only the parent coaching model showed significant impacts on student outcomes. Parent coaching alone with no instructional coaching was therefore the most cost-effective of the three treatment conditions for improving student outcomes.