This isn't what the rest of these comments would indicate (which say that people that get into top schools are fundamentally more qualified and intelligent than people that do not)
Your comment is the only one in this thread that uses the word "fundamentally." The other comments I've read suggested that school can be an indicator of talent/diligence/etc. especially in the absence of a lot of other signal. It's also true that Big Law and Big Management Consulting are pretty educational pedigree focused especially for new grads but that's not everyone.
OK, but it's a pretty big indicator, and apparently justified in being so because the people at top schools are just that much better than people like me.