I don't think that's the case at all. "Smart" and "hard working" are relative terms. Most "smart" kids aren't taking quantum mechanics in high school and most "hard working" kids aren't putting in 14-15 hour days in high school. You don't have to cheat to get to the top--you just have to have your shit together when other kids are focusing all their efforts on getting laid.
That said, the incentive to cheat is certainly much higher these days, between the 15 hour days and rigorous course loads, than it was 50 years ago before SAT tutors and numbers-based admissions; back when just being able to pay the $$$ for a top preparatory school basically guaranteed admission into Harvard and Yale: http://www.nytimes.com/2005/11/06/books/review/06brooks.html... ("That year [1950] 278 students from elite prep schools applied to Harvard and 245 were accepted. The acceptance rate from Exeter and Andover was 94 percent.").
That said, the incentive to cheat is certainly much higher these days, between the 15 hour days and rigorous course loads, than it was 50 years ago before SAT tutors and numbers-based admissions; back when just being able to pay the $$$ for a top preparatory school basically guaranteed admission into Harvard and Yale: http://www.nytimes.com/2005/11/06/books/review/06brooks.html... ("That year [1950] 278 students from elite prep schools applied to Harvard and 245 were accepted. The acceptance rate from Exeter and Andover was 94 percent.").