Well, the M.O. of the Percy killer was like 5 a.m. because he broke into another home the day before around 5:30 a.m. Another home invasion (Wacker, in winter, '65) he was thought to be present at was probably early morning, too, because the family was asleep at the time.
Valerie Percy neither lived in Barrington nor went to high school there. She lived in Kenilworth, and next door in Wilmette, both are 23 miles from Barrington, prior to that. Both villages are served by New Trier high school, from which she graduated.