On this week’s SELECTED SHORTS, we're going to hear stories about students and schools that abandon the usual rules to follow their own, unusual, codes of behavior.   In "Singin' in the Acid Rain," by Patricia Marx, performed by Katrina Lenk, it’s recess at a post-apocalyptic school.  Marx talks with Meg Wolitzer about the story and her unique brand of humor after the read. The class in “The School,” by Donald Barthelme, performed by Laura Esterman, is facing a difficult test; and young love is framed by larger issues in "Melvin in the Sixth Grade," by Dana Johnson, performed by Nikki M. James.   We hear from James about this nuanced rite-of-passage story.