A pair of lawsuits filed Monday by several fraternities and sororities challenge sanctions that Harvard University (MA) imposed on unofficial clubs that have played a longstanding role in the campus’s social scene. The lawsuits, in federal and state court, claim the university discriminates against students based on their gender and their membership to single-sex organizations. Harvard approved sanctions in 2016 and completed them last year against students who belong to single-sex fraternities, sororities and the secretive all-male groups called final clubs.