Broad generalizations about the public schools are not helpful. Yes, there are many schools that are not up to standards or outright awful but that does not mean all of them or even the majority.
I am subsitute teaching in my area and the schools I have worked are all excellent with good kids, devoted teachers, lots of help for kids that struggle for whatever reason. So the concept that since some schools are bad and the average test scores and grad rates are brought down due to them is just not the right approach. The poor schools need to be identified and corrected and the schools that are performing need to be left alone. I would love to see how the schools rate if you left out the problem schools in the averaging.