Unleashed - Jennifer Hartz - Bog

When six high school students at an upscale private school in Pittsburgh discover the demonic legend of the school's origin is actually true and obtain amazing superpowers as a result, they unwittingly unleash the demonic Horde.
Mike has a happy-go-lucky attitude and astounding athletic abilities that make him popular while twin sister Shelly is his opposite with her shyness. Cooper, crippled, considers himself a freak. Maggie is artistic and eccentric while Jimmy is a brooding heartthrob. New girl, Caitlyn, rounds out the group, though she can't escape the sense that she doesn't belong.
As a team, the teenagers need to figure out how stop the Horde before its evil spreads through the school and beyond...all while somehow keeping their ever-growing powers a secret.