Yes, he is a dual US/Canadian citizen.
And my question is if he graduated from a Canadian high school, I understand it would simply be treated as paying as an out-of-state resident. Financially, that is the case but what about the likelihood of him getting accepted in the first place? Would it be the same as if he graduated from a US high school and just went to college in a different state, or is it a whole different situation if he were to graduate from a Canadian high school?