High school years are about trying to figure out who they might be and become in the larger world, where they fit or will fit into the larger picture, who they will "become". As parents we can get anxious when we see successful children make poor choices, or drift with peers that seem as though they are doing that. But your son will need some room to talk with those he chooses. If he is actually not attending classes, becoming involved in drugs or alcohol, or increasing in risky behaviors, he then may well need intervention with school staff and possibly therapeutic support; having other adults/professionals involved, if it comes to that, can be a good reality check for teens.

His developmental step is to experiment with different viewpoints, learn, and become invested in the outcome; to become more independent. So, reflecting your belief in him, not condemning outright who he hangs out with, may increase his receptiveness; you can then reflect matter-of-factly, non-judgmentally, the changes you see happening, and outcomes (including interventions if needed) likely. Let him know you are there to support him, with whatever it takes, as he navigates tough years and hard choices. Good luck.