I was disheartened to hear Chris Hayes on C-SPAN say that the educational "reform" movement is "winning the argument." That's not to say they're winning on any factual level, Hayes meant that in terms of public debate, anything short of blaming the teachers means supporting the status quo.
It's worth noting that this scapegoat has resonance for a reason, there's an emotional appeal for blaming the teachers.
The Poverty Problem
The US education system isn't broken, it's being disrupted by poverty. As the Programme for International Student Assessment (PISA) test shows the United States ranked in the low 20s but at the same time it has some of the highest child poverty in the industrialized world.
When the effects of child poverty are factored in, the US actually outperforms every other country in the world. That is, all things being equal, we still have the best education in the world: an area with 10% child poverty in the US will, on average, do better than an area with 10% child poverty in Finland.
PISA Test Scores and Child Poverty

While the struggle with being poor has an obvious effect on learning, it also has effects for funding. Schools that have a higher poverty rate will have lower funding for the schools because of a lower tax base.
Total Per-Student Expenditures Versus Student Poverty Rates for U.S. School Districts with More Than 1,000 Enrollment

Indeed, these problems have been expanded by education policy and increases in poverty following the recession.
Bad Teachers
This leaves a problem, if it's objectively shown to be poverty then why is there an effort at demonizing teachers, or rather, why assume people would believe its the teachers that are the problem? It's the dominant position, everyone from Fox News to Jonathan Alter thinks its the teachers fault. So, agendas aside, why even push the story?
The answer lies in the anecdotal and emotional experience of people. Lets face it, you've had a bad teacher in your life. The problem is that one bad teacher is out of dozens of good (or at least adequate) teachers. Thus it's wrong to assume that someones personal experience accounts for a national epidemic.
Unfortunate the media does just that, it takes a personal experiences and turns it into a national problem. As a Newsweek article makes clear:
In most states, after two or three years, teachers are given lifetime tenure. It is almost impossible to fire them. In New York City in 2008, three out of 30,000 tenured teachers were dismissed for cause. The statistics are just as eye-popping in other cities. The percentage of teachers dismissed for poor performance in Chicago between 2005 and 2008 (the most recent figures available) was 0.1 percent. In Akron, Ohio, zero percent. In Toledo, 0.01 percent. In Denver, zero percent. In no other socially significant profession are the workers so insulated from accountability.
What Newsweek apparent forgot is that "In no other socially significant profession" are people exposed to dozens of such professionals. People don't just choose one teacher all their life like they would a doctor or lawyer, they go through numerous upon numerous ones. Imagine going through 20 mechanics or 20 doctors or 20 lawyers, chances are some of them won't be top notch.
Or more importantly, where's the evidence that those places needed to fire more teachers? As NPR points out, even when it's really easy to fire teachers (like, "at the click of the button" with virtually no documentation easy) many school principals don't do it.
What is to be done?
The important thing to remember is we're not dealing with an educational problem so much as a child poverty problem. That's why most "reforms" have little to do with improving education and are just done as a means to undermine it.
For instance, one favorite "reform" is charter schools, even though studies find that charters on average do worse than public schools.

If we want to get serious about education we should be fighting the cause of the problems, not making them worse.
Edit: A lot of commentators brought up good points on teacher tenure:
(A) Tenure isn't a guarantee to not be fired, it's to not be fired without just cause as well as the teacher being represented during the process. Prior to tenure a teacher can basically be fired on the spot.
(B) Those that get tenure are usually the ones that are the best and endured enough to be proven to be good teachers. Those low firing rates are because being a public school teacher is one of the hardest jobs out there and most leave teaching after 5 years leaving the good ones.
(C) A lot of bad teachers aren't directly fired but persuaded to retire. It's another reason why statistics for firing are so low.