Pretending to be someone they are not in an effort to impress admissions isn’t going to earn any points when evaluating the application. The officers want to know more about your student, who they are, what is important to them, and why they want to attend their college. They can’t get that information if your student can’t be himself in the essay.
If you want to keep your sanity and avoid unnecessary conflict over the college essay, take my advice and consult the essay experts on Twitter. Essay experts can provide all kinds of wonderful advice for your student (advice he will listen to because it's not from you). And if you're so inclined, they can work with your student to craft the perfect college essay.