Good and Bad at Games (1983)

The story, told partly in flashback to 1968, concerns a clique of English public schoolboys who bully and humiliate an unpopular younger pupil (Cox) who is 'bad at games'. Ten years later Cox uses the naive and equal outsider Niles, who is only included in the clique because he is 'good at games', to find out more about the lead persecutor (Mount), in order to exact revenge

Unfortunately the movie Good and Bad at Games is not yet available on HBO Max.