“…The program was developed during a multiyear iterative development process . A series of studies conducted during the development process indicated strong effects on vocabulary learning, with more moderate effects on comprehension (Greenwood et al, 2016;Kelley, Goldstein, Spencer, & Sherman, 2015). Subsequently, a cluster randomized design trial was conducted in 32 preschool classrooms with 195 participants (Goldstein et al, 2016).…”