Not
all engineering schools require admission to the major at the time of matriculation.
Some have gone to a professional-school model, where students APPLY to the major at the end of sophomore year, and until then, they are "pre-Eng" majors who take gen ed requirements for the institution as well as those engineering specific courses.
I'd recommend that he look at state flagships with a strong engineering program
and a strong science research component.
That way he can explore those things that he is most likely to find engaging and interesting, and can shift by making small changes rather than a huge one like switching to a new institution.
Engineering and Science, unfortunately, have less overlap in coursework than is ideal from a student's perspective. So in that respect, asking both professional engineers and scientists why they chose one thing OVER the other... whether that was the right choice for them, what they find to be generally true of individuals in their own discipline on either side of that divide, etc. Job shadowing, but with a list of interview questions, I guess.
DD did that and quickly realized that while engineers work on interesting problems, she is emphatically NOT one of them, because her brain simply doesn't work that way. She's a scientist instead. I personally tend to think of this as a forest or trees orientation to problem solving.
Scientists tend to see patterns in forest and sometimes get caught staring at one tree, and engineers tend to see patterns down in the trees and engage in breaking a trail through them without getting lost in the larger (or smaller) detail. Of course, each approach has distinct limitations and disadvantages. Scientists can take a year to plan HOW to build the trail that takes an engineer less than a month to construct, and engineers can miss the fact that they've just created ten miles of rough trail next to an existing paved one running parallel ten feet away, but there you go.
It's a matter of figuring out which mindset one is more suited to so that you find your tribe.
ETA: I love Michelle's advice above-- and concur strongly that interdisciplinary fields are especially well-suited to those at high cognitive ability since they value the idiosyncrasies and polymath tendencies that are so common in such individuals.
