Using moderated nonlinear factor models to adjust for differential item functioning in the Student-Teacher Relationship Scale from kindergarten to Grade 6

Prior research has demonstrated that children form developmentally salient relationships with teachers and that these relationships are uniquely predictive of subsequent functioning both in and outside of school. However, prior work estimating trajectories and predictors of teacherstudent relationship quality has failed to test and adjust for bias in questionnaire items. The present study used longitudinal data from the NICHD Study of Early Child Care and Youth Development (SECCYD; N = 1140) to test and adjust for measurement bias in the Student -Teacher Relationship Scale (STRS; Pianta, 2001) across grades (K - 6) and sociodemographic characteristics (i.e., birth sex, race/ethnicity, family income -to -needs ratio, and maternal education) to generate less biased estimates of trajectories of teacher -student relationship quality. Results identified differential item functioning for three of seven STRS items assessing conflict and three of eight STRS items assessing closeness, with items functioning differentially across child grade, birth sex, race/ethnicity, and maternal education level. Comparisons of growth models using non -adjusted and adjusted STRS scores highlight substantive differences between scoring approaches, such that the effects of race/ethnicity, maternal education, and maternal sensitivity on teacher -student relationship quality were masked prior to adjusting for item bias. These findings demonstrate the importance of testing and correcting for item bias in questionnaire -based assessments of teacher -student relationship quality to ensure valid conclusions.