essay is one of the most effective and fair ways to look at top kids beyond the numbers... A single AO could not make a final decision when the applicant pass the filter...AO/Admissions Committee look for best kids for their school campus and their (and the country's) future... it is a very seriously business in elite schools... (by the way, your S19 should try GT but the essay(s) and LORs are crucial for his case...GL to him)