It's not about money, you're the one who just thinks about money. Maybe, by your logic, if someone gave you $100 now, you'd become smarter and look wider... but probably not.

Sorting into better highschools and worse ones, and better classes and worse was done even back in my times, in what used to be yugoslavia, with communism, red stars and a dictator. You want better kids to excell as much as they can, and you want the stupid kids to at least learn to read and write for their boring communist factory jobs for the next 40 years, even if they never get to learn how to solve differential eqations... if you keep the kids together, the stupid ones still won't be able to do basic math and there would be no time left over for the smarter ones to learn more. There was no correlation between money and stupidity of kids.

Some kids are smart enough to become engineers, some can barely read, there's no need for them to be in the same classroom.