The burned out T-8 fluorescent lamps have recently been re-lamped in my science classroom, and one of the fixture's refractor was not latched properly. As a result, today, it opened up on its own during class.
Also, some of those fixtures in that room have dead ballasts, but there are two ballasts in each fixture, one operating the outer two lamps and another operating the center lamp, so those fixtures are still producing light from the other lamp(s). These aforementioned fixtures have a sticky note placed inside, with something like "BAD BALLAST" written on it.