One, we as a nation don't properly demand our kids get educated. We get slaughtered by the international community when it comes to this. We excel in nearly every negative statistic, teen pregnancy, drop out rates, etc.
Two, unions have a tendency to restrict the ability of competition in school access. There are dozens of places where charter schools are literally sending crying kids/parents away because they can't increase access to their programs. The greed of some of the union leaders damages the image.
Three, qualifying the value of teachers is tough. Especially in cities where 50% of the students don't even graduate high school. What is the difference between our situation and other countries?
Unions get blamed a lot (and in many ways rightfully so) simply because people are trying to reconcile all the issues.
Frankly, I don't think any of this can be solved with out culture's obsession with the school/sport marriage. Not to mention the insane amount of kids who don't have proper parental influence.