This may be a good time to start setting reasonable expectations. Half of the kids at all of these schools are going to be in the bottom half of the class. Most have probably been in the top decile up to this point.
Some will have top scores in international math contests. Some will be insanely talented musicians. Others will speak 5 languages fluently. This is a milieu that can be really intimidating if a kid feels like these are kids he has to compete against.
So it’s important to change the conversation to one that focuses on being one’s best self and supporting others in being their best selves, about being a good community member, etc. It really needs to focus more on him achieving his goals and not defining those in terms of others.
Really, this is a hard mind shift – not just for high schoolers. But as a parent, you play an important role in this.
Have him take a look at the book “That crumpled paper was due last week.” He’ll probably see himself in some of those scenarios and see some strategies that might help him. But I totally agree with @skieurope , most kids don’t show up at BS with these skills intact. Perfectionism is also likely to give way to efficiency.