Having spent my entire career in education (both union and non-union), I honestly believe that the unions, especially their leadership, deserve a small part of the blame for failing schools. But it's not for the reasons many would expect and it has nothing to do with money (see Wash DC) spent per pupil.
Most teachers care deeply about their students and go beyond the pale to help them succeed. Unfortunately, there are so many foundational and systemic hurdles to clear that the classroom teacher's task is almost insurmountable...especially in urban areas.
A few years ago I was sponsoring a luncheon for about 70 Language Arts Supervisors in NYC. After my presentation, we opened the floor for questions. Eventually, the discussion spiraled into a conversation about teacher frustrations and concerns.
Most were very hard on themselves and worried that they were letting their students down. At this point I said (paraphrasing) "I emphasize with your frustration but you're being too hard on yourselves." I further explained to them that, " I've been in schools all across the country and I think that I've identified the root of the problem. Not to be over simplistic, but if you find a way to fix the American family I think you'll discover that the majority of problems within your classrooms will vanish."
Obviously, identifying the root cause is far easier than solving it and probably not appropriate discussion for this board. I will say this...imo, government is not the answer, it is a big part of the problem.