She’s only applying to boarding schools that are near impossible to get into.
If she were applying to “whichever boarding school that (she could) get into” there’d be schools with a 50% admit rate on her list.
While it may be that their reasoning is that the local/current school is good, I would really like you and @pearlescentrose to rethink what is a “2nd rate boarding school”, because frankly you’re getting a bit offensive.
Many of these “second rate schools” offer as high quality educational opportunities as the “best” schools - and in some cases, even better opportunities, depending on the applicant.
And as some have pointed out, going to these “best” schools does not necessarily give you an advantage when you apply to Harvard. (Not that Harvard is a goal for my child. Thank goodness, or we’d have to disown the kid.)