A manhattan dad nearly choked on his Wheaties when his 14-year-old son timidly asked: "Dad, do I have to wear a dress to school?" No joke. These conversations went on in kitchens and living rooms around the city, as a top school that educates learning-disabled and autistic children staged a student production of "La Cage aux Folles" -- a cross-dressing, limp-wristed, gay comic romp whose main characters are a pair of "married" men. (snip)the kiddie version of "La Cage" was cooked up by the executive director of Child School, a private institution on Roosevelt Island that takes on youngsters from...