Start now on selling the idea of forming His List that reflects his interests, values and priorities. You never see a list that says this, but Julliard is a better school than Harvard, and Harvard might not even be top ten… for musicians. Lots of lists go sideways when you start getting specific and odd names start appearing: Purdue (engineering) or BYU (accounting) or Spelman (HBCU) or Hope (Christian) or UofMD-College Park (LGBTQ+) and lists go on and on and up and down and over there. So start looking into what and where and how he wants school to be for him.
A good way to cultivate that thinking is to get him out of his comfort zone a bit. Emphasize ECs chosen because they’re interesting rather than how they look. Look at things many kids don’t consider like ROTC or campus ministry, encourage him to go out for a play or even a musical, maybe join a no-cut sport. My son didn’t make the 9th grade baseball team at our jock-factory high school, so in 10th grade he and his friend went out for tennis in the spring. Good Lord they were terrible, but they had more fun than anyone else. He was about 6’5", 160 lbs and ended up playing JV teams that were predominantly freshmen, laughing at his own mistakes, really laughing at his doubles partner, complimenting the opponents and usually getting them in his spirit of the game. He didn’t go back out junior year because he had ACL surgery that winter, but the memories are awesome.
High school is more than getting into a famous school. It’s discovering who you are so you can pick a college that’ll help you grow to your full potential, as you. If your son is a solid student maybe he’ll thrive being the biggest, best fish in his middling-sized pond. (And the financial aid might improve too. 
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