How do Canadian marks get converted into American GPA?

My son is in a Canadian high school, but is planning on studying in the US, as he is also an American citizen. I am aware that a classification of a 4.0 or “A” isn’t the same in Canada as it is in the States. For example, a 90% in Canada (at least Ontario) would be an A but in American high schools it would be a 3.67 GPA or an A-. So my question is that do American schools convert or adjust high school marks if they’re from a different country?