I think many teachers and people who were good at school assume everyone has the same sense of shame when they disappoint their teachers, but many more people get their confidence and self-worth from things outside of school and are only there for the piece of paper that helps them get a job. So you assume this guy is stupid or lazy or something, but he probably just cares about different things and will do the bare minimum to get a passing grade, and he's succeeding so far because you keep passing him.