I went to boarding school (in the late-80s). I will say the college outcomes will not be much better than a rigorous magnet. Many of the un-hooked Ivy league admits from places like Phillips or Andover will still find a way to get to the Ivies without these schools. A lot of the Ivy admits from these schools are from legacies who have been prepping long before 9th grade. They've either been in the prep-school pipeline since kindergarten (either for sports, arts, debate, engineering, etc.) in addition to being legacies. Or, they are legacies with deep pockets. Those spots will constitute the majority of the Ivy pipeline in boarding school. The minority of the Ivy admits from these schools will be ordinary non-legacy kids who have talent and drive to do well in competitions. So, if you are a non-legacy kid going to one of the boarding schools, you still have to stand head and shoulders above the hooked, legacy kids or the deep-pocketed legacy kids. I don't see the value. I enjoyed my time at boarding school, but I would have preferred being home with my parents.