The Winchester High boys lacrosse team did not have a lead in its Coaches Challenge Cup quarterfinal against Wellesley until the fourth quarter.Once the Sachems took the lead, however, they held on, prevailing, 7-6 on Tuesday, April 17 at Concord-Carlisle High School’s Doug White Field.Winchester (5-0) will play either Dover-Sherborn or North Andover in the semifinals on Thursday, April 19 at Lincoln-Sudbury High School(2 p.m.).