Un Buen Comienzo [A Good Start] was a professional development program implemented with prekindergarten and kindergarten teachers in Chilean public schools serving low-income families. In a randomized trial, the program showed moderate to large impacts on classroom quality but no impacts on targeted child outcomes. To unpack these findings, we examined intervention fidelity (IF) in both treatment and control groups. Specifically, the study examined (a) whether teachers in the treatment group showed greater fidelity to teaching practices prescribed by the intervention, as measured by dosage and adherence, at the end of prekindergarten and the end of kindergarten, than their control-group counterparts; and (b) whether language and literacy instructional dosage predicted gains in children's language and literacy outcomes at the end of prekindergarten and the end of kindergarten. IF data were coded minute by minute from videotapes of study classrooms collected at the beginning of prekindergarten, the end of prekindergarten, and the end of kindergarten. There were significant and large impacts of the intervention on dosage and adherence. Additionally, small but statistically significant associations were found between 2-year accumulated overall program dosage and children's reading and writing skills at the end of kindergarten. Results reveal that teacher practices changed in response to the intervention, but that increases in time spent on language and literacy instruction were not very substantial. This pattern may explain the absence of an overall impact on children's skills in the experimental study. Findings have implications for the design of both future preschool interventions and IF studies.

This study used Latent Class Analysis to identify groups of children exposed to similar Home Language and Literacy Environments (HLLE) and explored whether belonging to a given HLLE group was related to children's language and early literacy growth from prekindergarten to kindergarten. Participants were 1,425 Chilean mothers and their children (M age = 52.52 months at baseline) from low-socioeconomic status households. Four HLLE groups were identified, which were associated with different trajectories of language and early literacy development. Children from groups whose mothers either read and talk about past events with them or teach them letters in addition to reading and talking about past events, showed higher relative vocabulary and letter knowledge. Implications for research and interventions are discussed.

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Coordinated Joint Engagement (CJE) is a behavioral measure used in the infant-caregiver interaction paradigm to measure joint attention. To know how mothers scaffold infant attention to prompt joint engagement states, this study attempted to determine (a) which specific maternal Attention-Directing Strategies facilitate CJE in mother-infant interactions and (b) how Attention-Directing Strategies precede a range of infant engagement states. Free play in 33 low-SES dyads was analyzed sequentially, a method that reveals temporal relations between the behaviors involved in an interaction. Maintaining was the only strategy that preceded CJE, and Introducing and Redirecting preceded infant Engagement with Object, Onlooking, and Supported Joint Engagement. The results point to the scaffolding role of Maintaining and the mediating role of Introducing and Redirecting maternal strategies. To understand how low-SES infants attain CJE is important given the relation between joint attention and cognitive development. Implications of the results for interventions aimed at reducing socioeconomic inequities in early cognitive development are discussed.