Taking a leaf out of Frank Herbert's book:
“Muad'Dib learned rapidly because his first training was in how to learn. And the first lesson of all was the basic trust that he could learn. It's shocking to find how many people do not believe they can learn, and how many more believe learning to be difficult. Muad'Dib knew that every experience carries its lesson.”
Coming into school, students seem to be bombarded with knowledge before they even know what to do with it. Within days, there's a whole load of content you need memorized, and you're expected to progress at the same rate as all the other students, whether or not it's actually true. The ones who get bad grades think they're dumb and get discouraged, and that is far more damaging than low IQ. Learning techniques and study strategies were never something I learned in school, and they are critical for many people to succeed. Referring back to ZenRaiden's answer, open-mindedness is also neglected, despite how essential it is.
Frankly, I think the whole education system is flawed almost irreparably. Everyone is just way too different. Going into Grade One, I was about 2 years ahead of my classmates since I had been at a very good school for Kindergarten. By Grade Three, I had entirely lost my advantage. The nerds, the sporty kids, and everyone else just get stuck in the same class and learn the same things in the same way. People get taught things that they don't want to learn and that won't help them in their career. Another big factor here is all the connotations associated with school as a result of this generalization. Despite a young interest in science, the fact that I learned it in the same place as Social and English killed it for me, and I was unable to reacquire that interest until high school. (I'm glad to say that I no longer despise English and Social Studies) Yes, there are advanced schools for particular subjects, and that's a very good thing, but I think the whole system needs to be organized more like that.
Anyways, I am highly open to critique, feel free to provide constructive criticism on my answer if you have a different view or a more experienced and tested opinion.