The National Council on Teacher Quality conducted a study recently which graded our schools from A-F. The grading was based on schools' ability to retain good teachers and fire bad ones, among other things which included student performance.
South Carolina recieved a B-, the highest grade in all 50 states. They earned this grade because of their ability to effectively fire teachers who can't teach. Currently most states have laws regulating everything involving education.
These laws tend to protect even the bad teachers, which has become a problem. Also, evidence from the study shows that states that don't give incentives to teachers who produce smrater students could be to blame for their lack of improvement.