This is an interesting one and one of my favorites. It combines the story of a boy with unknown heritage, magic, and eventually a greater mystery of the world.
Shirone is found abandoned as a baby in a commoner couple's barn and they raise him as their own. Growing up he is fascinated by magic, something for which the common folk don't have the aptitude. Discovering his spirit zone, and therefore talent with magic, on his own, he strives to attend a magic academy for nobles only.