Is he a US citizen?
Regarding his GPA (which is better than ‘medium’), does he have a high level of rigor in his course curriculum (honors/APs/accelerated math)?
What is his class rank/how does he compare to classmates wrt GPA and ECs?
Certainly continue the math competitions, and USAMO qualification process, those are good ECs.
Generally, (assuming he is a US citizen) students apply to several reach schools, 4-6 match schools, and at least one affordable safety. Budget dictates the college decision for many students, so best to define that as soon as possible.