Lakeside’s most famous alum is probably Bill Gates. Who, as brilliant as he is, also came from an “old money” Seattle family. His father was a founding partner at Preston, Ellis & Gates, one of Seattle’s most elite white shoe law firms in its time in the 60s, 70s and 80s.
I’m guessing that the Lakeside of today is more of a meritocracy than many of the elite east coast prep schools. Seattle has so many brilliant tech engineers from all over the planet working at places like Microsoft, Amazon, and the many other tech firms who put their super-bright kids into Lakeside. I expect that is why it looks different from the typical east coast prep school that is likely to be more WASPy and dominated by kids who’s parents are in finance, not tech.
Of course I expect all of this is because the top Ivies and other equivalent privates like it that way. These sorts of schools operate like minor league farm teams for them, producing a steady stream of top recruits. It would be harder for Harvard and Stanford if they had to only pick through public school applications, mostly prepared by the kids themselves.