Because he doesn't have kids in a decent USA school system. I am using the math as an exemple, there are 4 different level books for algebra, geometry and other topic. The top level in our school system that only 10 kids from 200 kids could take it and only half get B or up. And math teachers usually are math major from top 20 colleges and high school usually has one math professor from a top 30 colleges. Of course, our school system is also one of the best in our state, Budget is $20000 / student / year.
I read the math book from my son's school and it give very clear explaining for the questions that person listed, acturelly helped me to understand a lot of math questions I don't know before.
