Class size

I know what you mean about the math and humanities genes. Funny thing is genes hide and appear suddenly so don’t be surprised if your son suddenly can do Math more than he’s used to showing. It takes a small trigger like a good teacher or an inspiration. My DS is also better wired with Social Science and English too it seems but also enjoyed studying AP Economics and did fine in AP Cal and AP Stats in high school. Kids change sometimes, suddenly. My DS thought of doing History or Cyber Majors at USNA. He did well in both in his Plebe year finishing with A’s. But then he changed his mind to Quantitative Economics that requires more Math but with a focus on social science discipline in economics applied math and finance. NROTC requires only 2 classes of each Cal and Science classes or 4 semesters of each Cal and Chem and Physics at USNA. Takes just little more work with desire to learn. I remember James Cagney a Stuy Alumnus. We talked about him among other famous grads. It was fun talking about this.

Coming back to OP’s question on class size matters. Yes if you’re coming from a very small school. You may need to demonstrate a stronger ACA performance vs. coming from a larger school. Your 300 is a mid size. You should really focus on doing what you enjoy the most and volunteer in leading activities if you’re not a CPT but try to hold an officer role. Choose few activities you really like and Best to stick to it for long time as early as in middle school and go deep through senior year. Otherwise volunteer and make impact to your community you’re serving.

I appreciate your advice and enjoyed reading your DS experience. Thank you.
The number in our high school was TWO! (Homeschooled twins)
Fierce competition for honors! Valedictorian, Class President, graduate at top/bottom of class ;)

There has been a trend toward non-traditional schooling in U.S. Many more homeschooled and a big increase in online schooling, especially with athletes. I would not eliminate the possibility that some outliers come from online schools in states/districts that aggregate class size on a broader basis than a single traditional school.
In some ways, I guess you could say my twins had a class size of literally hundreds, if not thousands. They took some cyber charter school classes (and actually got a diploma from that school), AND attended two local universities, starting when they were 16.