The value of coproduction—the joint productive efforts by regular producers, such as teachers, and consumer producers, such as parents, in helping children to learn—has been recognized for some time. However, strong empirical evidence of how these benefits can be achieved is scarce, and recent research has found mixed results. A new randomized field trial replicates elements of previous studies and extends them by using an additional age-appropriate outcome measure. Methodologically, the results illustrate the challenges of carrying out replication studies because when target groups change, outcome measures also often change. Substantially, the findings suggest that a government initiative providing parents with materials and information to enhance parents’ coproduction efforts can be extended to a broader target group of parents. Together, the findings illustrate how findings from single studies should be generalized with caution and the value of working systematically with replications and extensions.