Because so long Bloom's 2 sigma observation holds, pedagogy only matters at scale. In other words, it mostly affect the lower middle class and poor people. Good education systems can ensure that most people get educated. The elites and upper middle class are more than capable of giving their children an excellent education anywhere. Working class parents don't have time to babysit every single homework problem or to fix every gap and flaw in the school's syllabus by themselves.