No idea friend, smarter minds then me are needed to investigate this! I would guess it is very multifaceted, between teaching styles, staffing, the culture of learning, neighborhood makeups, home life, etc. Some things are not easy to address, if you have an area with a lot of students with bad home lives, school can only do so much to help, especially if the system is rigid and can't easily give extra non-educational resources to those students. If a student simply was raised to have a disdain for education, lack respect, etc. that is not something you can easily solve with just money. Are charter curriculums better for these situations? Those are the kind of questions we'd wanna check. I'm not gonna say it's just a case of well union DOE teacher = bad, charter teacher = good. There are definitely bad teachers, regardless of school, but it goes beyond just that.