We encourage him to reassess his course load (advanced placement and honors classes) and the many extracurricular activities he's involved in, but he's stubborn and won't consider those options. He's in way over his head and this is reflected by his negative attitude and declining grades. What can we do to slow him down without looking like we're punishing him?
Besides talking with him about how to relieve some of his anxieties, it might be beneficial for all three of you to speak with his guidance counselor. Are there any seniors with whom he is friendly and whose opinions he might respect regarding his dilemma? He's disturbed and worried that he's blown his chances of getting into a good college by not having a stellar junior year. These anxieties are contributing to his free fall and he doesn't appear to be able to use reason to bring himself out of this tailspin. He probably feels like he's failed you, too. In addition to his school counselor, I'd like to see him get some short-term therapy. Let me know of your progress.