Christopher Tiu sizzled for a tournament-high 40 points while Bon Syiaco and Paul Chua chipped in 12 apiece to lead Xavier to its fourth win in six games.
St. Stephen’s, which dropped to 3-3, was led by Kish Co’s 25 points.
Host UNO High School, meanwhile, improved to league-leading 4-1 with a 60-46 romp over cellar-dweller St. Jude.
Richmond Ng tallied 12 points while Richie Chong added 11 to pace UNO, winner of its last four games after losing its season opener.