My experience in elementary school with the confederacy is this. "They wanted slaves, they are bad." As I have gotten further in my education, this is not the case. Starting in middle school, we were taught more of a "while yes, they wanted slavery, they also wanted more things more than that, mainly states rights, so as a state could choose to be a free or a slave state." mentality.
I believe that most schools don't exactly give directly false information. I believe that schools tend to give the simplified version of history. They give half-truths. It's easier to simplify history into good & evil, than it is to give the full story. That's why the common conception is that the South was the brutal villain, and the North was the conquering hero.
People say the South shouldn't have seceded, but in reality, the South was doing exactly what the American colonies did, about 80 years before. They were rebelling, because the wealthy authorities in the North were taking advantage of them.
You are taught that the South supported slavery. You aren't taught that the North also supported slavery, and even exploited slave labor to fund wartime production.
You learn about Lincoln, and the Emancipation Proclamation, but nobody ever clarifies that the Emancipation Proclamation didn't actually cause any direct change, or that some slaves weren't freed in the North until closer to 1900.
You learn about slavery in the South, but they don't specify that only about a third of Southerners owned slaves, and that Northern businesses had no qualms about profiting from slave labor on plantations in the South.
People like to associate the South with numerous atrocities, but nobody ever discusses the various atrocities committed by Yankees. The rebels never burned an entire city to the ground out of spite.
People may say it was about states rights, but I ask you, a states right to do what? Others may say it was about freedom, but again I'll ask you, freedom to do what? The vice president of the Confederacy even supported the idea that they succeeded over slavery when he said: "Those ideas, however, were fundamentally wrong. They rested upon the assumption of the equality of races. This was an error. It was a sandy foundation, and the government built upon it fell when the “storm came and the wind blew.”
Our new government is founded upon exactly the opposite idea; its foundations are laid, its corner- stone rests, upon the great truth that the negro is not equal to the white man; that slavery subordination to the superior race is his natural and normal condition. This, our new government, is the first, in the history of the world, based upon this great physical, philosophical, and moral truth."
By and large the Confederacy was about Slavery. Any claim that it was about States Rights was nothing more than a purr word. Even so, in 2015, the concept of States Rights is obsolete in an interconnected world. There's no reason for an individual state to operate it's own little autonomous fiefdom in the middle of it's arbitrarily drawn borders.
The only reason it does is because too many Americans are irrationally paranoid that any government will automatically turn into the Dark Empire once it reaches a certain size.