The moderating role of assessment diversity and load on student outcomes

Assessment design is a critical, yet underexplored determinant of student academic performance in higher education. Drawing on the testing effect and cognitive load theory, this study advances the proposition that the positive effect of assessment load on performance is moderated by assessment type diversity, which imposes extraneous cognitive load through task-switching demands. Using large-scale administrative data from UK higher education (N = 707,288 student-module observations), cross-classified multilevel models revealed a significant positive main effect of assessment load on module marks and a significant negative moderating effect of assessment type diversity. Subgroup analyses demonstrated that this moderating mechanism was substantially stronger among non-STEM than STEM students, theorised through Bernstein’s distinction between horizontal and vertical knowledge structures. Robustness checks across three diversity operationalisations confirmed directional consistency. These findings offer theoretically grounded, empirically robust guidance for assessment design policy across disciplinary contexts in higher education.