These selective colleges are among those that appear in a Princeton Review sampling, “Great Schools for Mathematics Majors”:
Harvey Mudd
MIT
UChicago
Caltech
Harvard
Haverford
Hamilton
Bowdoin
Reed
Rice
Carleton
Grinnell
Macalester
URochester
St. Olaf
If nothing else, this list could serve to confirm some of your son’s current schools of interest.