As someone who has seen how this all plays out, (since my kids are grown) it does seems that going to “good schools” (as defined in other posts) does make a difference for the majority of students. Of course, there are always exceptions that can be argued both ways.
Even then, I can tell you that, regardless of what schools your kids go to, or how smart they are, the (now global) competition is fierce, and there are a ton of other variables that will ultimately determine their level of success.
When my kids were competing for their career positions, they found that most of their competitors had similar top notch academic backgrounds, and the determining factors in hiring them included far more than academic achievement.