I believe parental involvement is the most important factor. My daughter is entering the 9th grade and I've done the experiment of measuring how well she manages herself depending on our (her parents) level of attention paid to her school work. Based on her habits from the first through the eighth grade, she requires constant attention to ensure she maintains focus. When I lost focus and stopped checking her work weekly and making sure she reads/summarizes daily, her grades dropped terribly. If I stay attentive to her school work and study habits, she earns straight As. It's a little annoying, because that means the ability is there, she simply doesn't care if I don't care.
Her teachers have become only half of the reason she is learning or not, because many seem a bit bitter about the job. With some i get the sense that the change in demographics has surprised them and they don't know how to react to it. I feel like I do a fair share of educating and that I should really only expect the school/teachers to provide a curriculum and alternative perspective to what is heard in my child's family. Ultimately the family is responsible for educating the child.