The studies I have read on charter schools are all over the place. The assessment conducted a while back in Philly showed that these schools did no better than public schools with some exceptions. The way I see it, charter schools, like all private schools get a break because they cherry pick the best students; the ones with engaged families and so on.

Teacher Unions can be problematic, but the real problem based on experiences in my family(we have a lot of educators in the family) is district and school administrations. There are a lot of politically placed people in both types of positions and they're often more interested in protecting their privileges than in serving students.

Meanwhile, the overarching issue in US education is commitment and inequality. We do not make the commitment to funding our schools that we should and we tend to fund schools with local property taxes. The result is huge inequality in schools. Also, US culture really downplays the virtue of education. So much so that teaching is dismissed a profession.