This supplement will provide an opportunity to test the impact of child masking due to COVID-19 on adjustment among children attending preschool and kindergarten participating in the FRIENDS project, which is a multi- method, multiple cohort, longitudinal study. This supplement has clear theoretical, educational, clinical, and policy implications. Based on rigorous prior theory and research including some preliminary data related to the impact of COVID-19 from the parent grant, we propose to assess the impact of school-based masking on four facets of child adjustment that have been theorized to be critical elements of child development disrupted by COVID-19 pandemic: 1) academic competence; 2) behavioral and emotional adjustment (i.e., hyperactivity, aggression, anger, depressive symptoms); 3) social functioning (friendlessness, rejection, victimization, prosocial behavior); and 4) acute and chronic stress system activation. We will test the central hypothesis that although masking may introduce some new challenges for children and teachers, children experiencing in- person, masked school will exhibit social and academic adjustment that is higher than unmasked remote learners and similar to unmasked in-person learners. The proposed supplement will test the impact of child masking at school on adjustment among children attending preschool (Aim 1) and kindergarten (Aim 2), and evaluate potential moderators of these effects (Aim 3). In addition, we will examine whether parental masking practices, parental masking attitudes, mask-related conflict, and parent-teacher communication and support are related to adjustment among children engaged in masked, in-school learning (Aim 4). The sample is diverse in SES and race/ethnicity. We will use multiple methods that have been successfully implemented for the parent grant during COVID-19 (e.g., home-based saliva and fingernail collection for cortisol assays, direct academic assessments via zoom, caregiver and teacher reports via qualtrics). The current proposal will use state-of-the-art techniques for assessing all constructs, which have strong psychometric properties, enhancing the rigor of the approach. The approach is consistent with the existing parent grant and is a natural extension of the aims of that grant. Investigating the effects of masking on adjustment during preschool and during the transition to kindergarten will enhance our understanding of how to foster wellness and school readiness in the age of COVID-19; further, moderators will provide important insights regarding which children are most strongly affected by in-school masking. Finally, the examination of effects of parenting contexts will provide important insights regarding the conditions under which in-school masking may present challenges for child adjustment, which educators, policy makers and clinicians may then address. The proposed supplement will provide a rich dataset with opportunities for secondary questions related to COVID-19. The proposed project is well positioned to advance major “high-priority” initiatives of the Eunice Kennedy Shriver National Institute of Child Health and Human Development (Child Development and Behavior Branch).

PUBLIC HEATH RELEVANCE: Understanding the impact of child masking due to COVID-19 on adjustment among young children has clear public health, educational, and clinical implications. However, little research to date has investigated the impact of school-based masking on outcomes like stress arousal, peer relations, and academic competence among early childhood populations.