my kid is in a top private school. some of my kids' schoolmates are from China/hongkong, most of them ended up going very good college but not ivy-level school. a few are accpted by ivy, one got into princeton this year.
My point is that if the kid is prepared then good US private school will privide him/her good education but may not ensuring an ivy school, so if the parent's only goal is ivy then it could be disappointment.