If he continues with this type of results, he’s got an amazing academic&financial “safety” in McGill. It’s not the residential college experience students expect, more like grad school in a way, but they select based on grades and as a French citizen he’d get a huge discount compared to other internationals.
As a US citizen, since you moved after his 10th grade, you had time to re-establish residency, so that he can get the in-state tuition discount at his flagship(s).
What state do you live in?
Some states have exchanges with other states (WUE for the West, MSEP for the Midwest, ACM for the South…)
Some states are better than others when it comes to admission criteria, selectivity, academic quality, costs, and financial aid. If you’re in CA, NC, VA, you’re lucky, for instance, on all accounts. If you live in Pennsylvania, Illinois, AK… not so much, for a variety of reasons.