To learn well in school — and out — you need to feed your brain. As Dr. Drew Ramsey says in How Food Affects Your Brain (16 min), it needs zinc, magnesium, omega-3s, cholesterol, and more. In the video, he suggests foods to eat to obtain those nutrients.
For more info, read the books and Websites of Dr. Terry Wahls and Dr. Datis Kharrazian have better views.