A central task of educational researchers has been to uncover factors that improve student academic achievement. Research in both developed and developing nations during the past few decades has analysed the links between educational outcomes and school physical resources, teacher quality and children's demographic and family background. Importantly, research on teacher and school effects in developing countries has focused on factors such as human capital, economic resources and physical infrastructure, the so-called input factors in the "black box" production function model of school outcomes. Fewer studies have focused on the "softer" classroom process factors that might be seen as important mechanisms of the production function, such as teaching style, the quality of teacher-student interactions and student academic engagement.