Crenshaw High School, among Los Angeles' lowest-performing campuses, lost its accreditation this week, throwing into doubt the worth of the diplomas its future graduates will receive. The Western Assn. of Schools and Colleges, which accredits public and private high schools in California, notified school officials Monday that the campus had been stripped of its accreditation after failing to correct what it found were persistent, widespread problems. In a letter to the school, the association's accrediting commission said it had rejected the school because of "great concerns regarding student achievement, the implementation of a curriculum and instructional program aligned with California...