Several years ago, my reaction would have been an immediate and resounding NO!
Now before I go on let me say, the Confederate flag has been co-opted by racist groups, and has come to have a very negative connotation. As such, anyone with a modicum of cultural sensitive should refrain from wearing or displaying this symbol. Having said that, we have a Mort Kunstler print hanging in our home, that does have the Confederate flag in the scene. In it's historical context. Because the Confederacy is a part of our history, and a part worth remembering.
After spending five years living in Virginia, I learned a great deal about the Civil War, and how it emotionally and historically impacted the South and its residents.
Confederates in the Attic by Tony Horwitz is a fascinating book about the way the War continues to affect the South. I highly recommend it.
Anyway, the Civil War is a complex subject, and the North and South are not easily divided into "good" and "bad". The United States did not engage in war with the Confederacy to end slavery; that was a by-product of a war that was fought to return seceded states back into the fold, and establish this nation as a Union that could not be dissolved.
Northerners were no more likely to be less racist than Southerners. Abolitionist societies may have wanted to end slavery, but not for the purpose of welcoming blacks into white society. One group's purpose was to send blacks back to Africa (the country of Liberia was founded in this manner).
New western territories didn't want to forbid slavery so much as they wanted to keep blacks out of their new territories altogether.
Slavery represented an agrarian, plantation-based economy that was entirely at odds with the North's factory and wage-driven economy. Congressmen from the North and South found themselves at odds with each other on many issues.
Imagine this scenario: you are a citizen of a country, you pay your taxes, you follow the laws, you elect representatives. But your government makes decisions that you feel violate your basic rights, as you understand them. You begin to feel that your government is not only not working in your best interests, but is actively working against you. You meet with other like-minded citizens, and make the bold decision to declare your independence from such a government, and to establish your own country.
Now...did you start the Civil War, or the American Revolution?
Most Confederate soldiers fighting in the lines were simple and poor farmers, not slave-holding plantation owners. They considered themselves the true sons of the Founding Fathers, carrying on the tradition of rejecting a government that no longer met the needs of it's citizens. The average soldier didn't fight to preserve slavery any more than the average Northern soldier fought to end it.
The Civil War is a fascinating subject, and certainly worth reading about. In terms of the girl who wishes to wear Confederate gear to school however, I would side with the school. They are entitled to establish a dress code, and students are free to dress as they wish outside of school.
) and have taught you NEW hate words. Not to mention, people ask you if you can read and do math. All of this because you are from the South? 
), and seeing letters to the editor in the paper about we "Dang Yankees" who should just go home ("Delta is ready when you are") but these people are the *vast* exception in my experience. Although I miss home and much of what I grew up with, there is much I respect about the South--children are taught impeccable manners, and are expected--no--*required* to exhibit them. I can't tell you the compliments I get on my son when we go back home just because he says sir and ma'am--and that's mostly from his Southern upbringing. 
