At the Alaska Bead Company, twenty-five-year-old Emily Ningeok carefully weighs out exactly two ounces of craft beads, places them in a small plastic bag, staples a tag on it, and puts the bag in the "done" pile. Working as quickly as she can, Ningeok fills fourteen bags in half an hour. She is an excellent part-time employee who works hard and gets along well with her coworkers. Ningeok is mentally handicapped, and therefore, despite her skills and pleasant personality, is lucky to be working at all. While employment discrimination based on race, ethnicity, and gender has diminished substantially in response to legislative and societal changes, prejudice against people with mental retardation has stubbornly persisted and continues to infringe upon their civil rights.

About 3 percent of Americans are affected by mental retardation—one family in ten will be touched by it in some way—according to the Association for...