Abstract
This study examined the co-development of educational expectations and effort (conceptualized as indicators of individual agency) during secondary school and assessed their role as predictors of academic success, controlling for prior academic attainment and parental social background. Drawing on data collected for the Longitudinal Study of Young People in England (LSYPE), a nationally representative sample, the findings suggest reciprocal effects between expectations and effort, shaped by family SES and prior academic attainment. Agency is not a static construct, it is not fully determined by family SES and students adapt their functioning and choices in response to informative feedback loops.