This is a very common thing around here indeed, people don't like to admit to making an effort, at least regarding school, so lots just won't push harder, whereas others will just lie, saying they didn't study very much. Nobody wants to look like they made a great effort and then got an awful grade (fail).
That's a dead giveaway for a "fixed mindset" about intelligence. Studies show that people that think that effort is an indication of lack of ability will avoid effort to not look stupid, leading them to perform less well over time than those that don't have this mindset. See research by Carol Dweck et al.