In the present study, we tested the assumption that performance in a knowledge retrieval test would be lower in secondary school students with temporarily depleted self-control strength (n = 53) compared to secondary school students with temporarily available self-control strength (n = 56). After manipulating self-control strength, students were instructed to memorise the names and the functions of the human eye and to recall as many names and functions as possible following a one-min distraction task. The results supported our assumptions, as students with depleted self-control strength performed significantly worse in the knowledge retrieval task compared to students whose self-control strength had not been temporarily depleted. The results suggest that depleted self-control strength may negatively affect academic performance and hinder a successful academic career. The theoretical and practical implications of these findings are discussed.