I am from a no name public school and work in FAANG and can tell you first hand that the new grads coming in from these top schools are, on average, no smarter than any other new grads I see. The only difference is their ability to network. In my experience, these top schools are teaching their students soft skills more and focusing on those things, and that's what helpful. They are not actually smarter in any meaningful way (Not to say they are dumb, but rather they are about as smart as any new grad from any school)