Because that has happened and is described in Malcolm Gladwell's book Outliers, about a school in a poor area of a big city which has good results, and their secret is school every weekday and Saturday, starts early, finishes late, focused work.
I reject the notion that all kids should have high scores on their government demanded tests. It's easy to become blinded by flashy results. But remeber the tests you had to take in school. There were always two approached.
1) Study a lot, fill your brain with all the details before the test.
2) Just understand whatever it is you're doing.
Method #1 is hard, you have to focus, and you won't really learn anything either, al you will learn is how to repeat something you've heard before. It's likely that you'll forget what the test said you had supposedly "learned" within a year.
Method #2 is easy if you're smart, especially in High School, later on in life you actually have to practise
I'm saying that the market would produce what we demand, not what some social engineer deems fitting.