Colin Peirce's parents didn't think it was possible that their son could be elected Nevada Union High School's homecoming king. Denis and Nancy Peirce were just thankful when their son, a 17-year-old with Down syndrome, was named one of the three finalists. To see him riding in a convertible and waving in a parade-like procession at the Sept. 23 homecoming game, in front of the whole school and thousands more on hand, was something the couple never dreamed they would see. "What the student body did for Colin speaks volumes for what our school stands for," said Jennifer Victor, a …