Consumers of public school services often have only the vaguest idea of the combination of academic knowledge, physical education, vocational subjects, social engineering, and fun that they want for their children. Model selection is a bad joke. Before charter schools, public education offered two models. Other than the Independence Institute's Parent Information Center, school rating systems hardly exist. Parents know little about what their children are actually being taught, and less about other educational models.
Product evaluation takes decades.
Only years after graduation can one evaluate how good a job the school did. Schools that consistently produce a bad product often get the most money. Worst of all, the people who run the public schools have little real control over policy or personnel. That is in the hands of the teachers unions who run the school for the benefit of their members. Teaching is only one of many factors that affects student performance.