I have to disagree with the sentiment that it’s “normal for even a well prepared student to struggle at a top college.” I’ve had this discussion with my husband a lot as we were making choices about our kids schooling. My husband and I both went to a top College. Tippy top. I came from a regular private school. Had phenomenal teachers, small classes, huge emphasis on critical thinking and writing. He went to a “top in the state” (in one of the best states) public school. We had the exact same score on the sat. He was FAR less prepared for college than I was. I think there is an assumption that good test scores and AP scores are a predictor or at least an indicator that all is well. Frankly the AP tests were a joke for me (perhaps they have changed) but getting a 5 on them was far easier than any exam I took in highschool (and I am not a great test taker).
My point is to give background to the statement that schools differ a lot in the way they prepare kids for college. I second, third, fourth the idea that you should look at private school or boarding school. Your story about your older son will be compelling when they ask you why you are looking at private schools. You may be very surprised at the amount of fa you can qualify for.