Did you and your wife go to college? What is your line of work?
If you’re lower middle class maybe he sees college as a waste of time if his parents went and aren’t particularly successful. Stressing about grades won’t get you anywhere. It’s about the process not the results. Once you’re in the real world nobody is asking for your high school grades and they could care less if you were a high school athlete.
Let him know you care and treat your wife with love and respect. Create a supportive and loving home environment free from the stresses of the outside world.
Work on yourself, do things you enjoy, get a hobby. Your son is the age where he craves independence but is stuck at home under your rules for a few more years. Help him become more independent. Give him the tools to succeed. You aren’t going to be able to boss him around once he leaves the nest.