Well I feel like I have a unique perspective. My mom has worked in schools all her life (most of the time as a special education aide), all of my jobs have been in schools, my sister and most of her friends are becoming teachers, and I now work at the state Dept. of Education.
I have seen teachers who work hard and get blamed for problems that they did not create and could not possibly fix with the resources they're given. A lot of my mom's co-workers are like this, and I feel for them. This led me to blame the state for not providing them with what they need.
Then I lived with my sister for a couple of years while she was going to school to become a teacher. Her friends were over quite a bit and they often talked about their program. And I lost all hope in the future of teaching. The vast majority of them were in the program because they couldn't figure out what their major should be, so teaching elementary school was a fall back option. They were mostly lazy and unwilling to do the work. They said that they didn't choose a "real major" because it would have been too in depth and too much work, so they instead chose to broadly cover several subjects at a middle school level...their math skills are HORRENDOUS. I looked at the work my sister was doing, adding FRACTIONS, and she was complaining about it. And they didn't even come close to grasping chemistry or physics. My boyfriend was a tutor for many of these students and the stories he told would horrify you. And these people will teach our children? Wonderful. So I leaned more towards blaming the teachers.
So now I work for the Dept. of Education, and I see that a lot of the problems seem to occur at the district level. Corrupt superintendents and districts not willing to comply with laws seems rampant. People in my department are on the phone with districts every day arguing over what should be done. So now I lean towards blaming the districts.
I think that all of these groups contribute to the problem. The state lawmakers for making shitty budgets (or no budgets at all in California's case

), the teachers who aren't willing to educate themselves, and the district leaders who aren't willing to comply. There are of course good lawmakers, amazing teachers, and worthy district officials, but their hands are tied by the bad apples.
And ultimately, I believe that a lot of the blame is on the parents. One thing I've definitely learned at work is that if the parents aren't willing to fight for their kids' rights, nothing will be done to fix the problems. No one cares about their child more than they do, and it is their job to make sure they are getting the education they deserve.
Unfortunately, too many people are lazy. Not willing to put in the effort to do the "right thing," to care more about their constituents, students, employees, children, etc. There are always hardworking people, but it seems like the lazy ones overshadow any progress they may make.