Research documents that parental beliefs influence early investments in children, which, in turn, determine early human capital and, eventually, other skills children acquire in later stages of the life cycle, such as literacy. Our paper reports the results of an experimental evaluation of the LENA Start Program, a group- and center-based parenting program that teaches the science of early language development, models verbal interaction behaviors with children, and provides objective feedback to improve the early language environment. The intervention changes parental beliefs and affects the quantity and quality of parental linguistic input.