Rutgers has a fantastic reputation among corporate employers-- especially for math. That’s a great starting point for your son. It saddens me to think that he’d rather shoot for a school with a MUCH weaker reputation (some of the other posters have cited specific rankings from various organizations) if Rutgers could be affordable for you. I know it’s not a shiny “admit” for local kids- but companies across the country know the program very well.
Re: using his skills for good- Rutgers also has a very highly regarded department of political science, and some really fabulous institutes for various policy and public affairs initiative. Whether the subject is gerrymandering, voter suppression, cyber security issues with online voting, income inequality, participation in the workforce by various demographic groups, etc. you could do a LOT worse than a math/poli sci combo at Rutgers.
The best statistician I ever hired came from Rutgers. We initially targeted a PhD, but ended up hiring a guy who had just completed a Masters in applied math at Rutgers and we quickly realized he was better than many of the doctorate candidates we’d met. Undergrad and Masters from Rutgers, New Jersey kid- he was fantastic.
There are lots of other ways to use math for good- biostatistics, epidemiology if he’s interested in disease transmission and prevention; genetics, agronomy (some fantastic gains in yields of various crops around the world by using sophisticated algorithms taking into account weather, soil conditions, bacteria, etc.) urban planning, sustainability, oceanography (suddenly a cool field after decades of it being considered slow and boring), meteorology, transportation planning.
But for now- just knowing that he’s a happy camper using numbers is really enough. If he ends up at a large research university there are going to be dozens of courses every semester he’ll want to take and just not enough time!