Teachers not doing their job, parents not caring, students not caring, and certain politicians who act like "being smart" is a bad thing for the "elite media."
One quick example of a teacher with high aspirations that was emotionally defeated by apathetic students. My brother's senior year of high school, a college professor (with a Ph.D in English) came to teach. She initially was very demanding, assigning reading and writing assignments every week. But students were just NOT turning them in. Eventually, the principle approached her about the number of Fs she was being forced to give out. So she lightened up and now gives no homework at all.
So teachers come in with high aspirations, and the student body just won't give. Therefore, I think the core problem is parents. Parents are not raising their kids right and teaching them to value education. In some cases, it's because our wonderful system does not help single moms and they are forced to work all the time, and their kids suffer, and our society overall also, as a result. In other cases, some people have no business being parents at all.