Many school districts face the empirical challenge of monitoring program quality to assure that all children experience pre-K environments that foster early learning and development. Factors that are exogenous to classrooms (such as evaluation timing) may play a role in estimates of program quality and yet are not fully understood. This paper examines the role of timing in pre-K classroom quality as it was observed in practice by one of the largest school districts in the United States. In the 2015-2016 school year, New York City (NYC) observed 648 of its Pre-K for ALL programs using the Classroom Assessment Scoring System Pre-K (CLASS), giving each program an overall average classroom quality rating at one time point. (author abstract)