GREY'S ANATOMY - "Forever Young" - The ER is filled with teenagers after a schoolbus crash, Bailey treats a patient who was her high school crush, Derek goes out on a date with a fellow doctor, and Thatcher enters the ER looking for Meredith, on "Grey's Anatomy," THURSDAY, NOVEMBER 15 (9:00-10:02 p.m., ET) on the ABC Television Network. (ABC/RICHARD CARTWRIGHT) CHANDRA WILSON, PATRICK DEMPSEY