Hundreds of classes have been canceled and dozens more relocated as a strike by graduate employees at the University of Illinois Urbana-Champaign continues into a second week. On Tuesday night, graduate workers occupied the office of university president Tim Killeen. Strikers have a variety of demands, but one of the most contentious points focuses on the future of tuition waivers — and whether some graduate workers will have to pay tuition while employed in academic positions on campus.