At the link below are NEPSAC (New England Preparatory Schools Athletic Council) archived Track and Field results. It will show you times and results from many boarding schools, and if your nephew is competitive with these results, you can have him or his parents contact coaches at some of these schools to gauge their interest in recruiting him. Recruitment is important, especially if financial aid is required.
http://www.sub5.com/youth-pages/nepsta-d1/
Best of luck!