If you give people enough incentive to cheat, people will cheat:

Of all the forms of academic cheating, none may be as startling as educators tampering with children’s standardized tests. But investigations in Georgia, Indiana, Massachusetts, Nevada, Virginia and elsewhere this year have pointed to cheating by educators. Experts say the phenomenon is increasing as the stakes over standardized testing ratchet higher — including, most recently, taking student progress on tests into consideration in teachers’ performance reviews.