Seven days before the test, Stephanie Yeh stood in her sorority house and cried. An electrical engineering and computer science major, she was set to graduate near the top of her MIT class next month and start a six-figure job as a Wall Street analyst. Just one test, terrifying to her, remained. She, like scores of undergraduates at Massachusetts Institute of Technology, had been putting it off for nearly four years. But Yeh and the others have to pass this exam to graduate. She had to swim 100 yards, four lengths of a pool, without stopping. The problem: Yeh never...