Calculus was introduced around ages 17/18 (senior year, i.e. the last year of high school, aka 12th grade, or the 13th year of formal primary and secondary education that most complete, including kindergarten) at the locally-regarded-as-very-good US high school this "elder" millennial attended, and only for those seeking the variant of our high school diploma that was supposed to get us college-ready.

But it may have changed since then.