The developmental influence of sex composition in preschool classrooms: Boys fare worse in preschool classrooms with more boys

A multilevel modeling approach was employed to investigate the relation between sex composition and developmental change in 70 urban preschool classrooms. The research represents a unique contribution as (1) few studies have examined the influence of sex composition during the preschool years, (2) it represents the first research to use a continuous (i.e., sex ratio) as opposed to binary (i.e., mixed- versus single-sex) indicator for classroom sex composition, and (3) the sample represents an important and often neglected group (i.e., low-income children from urban schools). A series of HLM models were run, addressing the nested nature of the data (children within classrooms), and relating classroom sex composition to developmental change using the cognitive, motor, and social subscales from the Child Observation Record (COR). Overall, there were no main effects at the classroom-level for sex composition. However, a cross-level interaction indicated that, while girls’ development was not influenced by classroom sex composition, boys in classrooms with proportionally more boys fared significantly worse in terms of development as assessed by combined score on the COR. More specifically, this interaction was significant when predicting the COR cognitive subscale, but nonsignificant when predicting the COR social and motor subscales. This was true when controlling for the number of students at the classroom-level, as well as child's age and baseline ability (i.e., Time 1 COR) at the child-level. Implications for early childhood education policy are discussed.