The drop in school grades and difficulties in psychological adjustment that occur when students make the transition from elementary to middle school can result from a mismatch between the characteristics of early adolescents and the design of middle school schedules and classroom practices, known as poor
a. developmental fitb. core curriculum fitc. stage-environment fitd. understanding of adolescent development

   C. Stage-environment fit

Explanation:  When students move from elementary to middle school, grades fall due to poor stage-environment fit. According to the theory of stage-environment fit students achieve better results and get better grades when the work environment meets their needs and according to their developmental age. Conversely, when this is not the case, they perform poorly with poor grades. So when students move from one stage to another during school, as in this case from elementary to middle school, then the work environment needs to be adjusted to suit the psychological needs of that age, as well as to respond to the psychological changes that occur at that age and due to changes in work environment.