"That depends on the nation in question. Most nations are mono-cultural. Some nations/cultures put a premium on education as a means of success. Some don't. In america we have numerous cultures/sub-cultures. To be fair if you want to compare us to say, germany or japan you would only include those cultures that value education. Think in terms of any of our middle and or upper class americans irrespective of their color. We would compare quite favoribly."
In other words wealthy white and Asian American kids do really well. Black and Latino kids don't as a general rule.
My kids went to charter schools along with the kids of university faculty. All white and Asian. Charter schools are fine, but teacher's unions hate them.