The 100 by Kass Morgan

Centuries in the past a nuclear war devastated Earth; the only surviving occupants living in spacecrafts far above the radioactive mass. Fast forward to the present and one-hundred juvenile delinquents are being sent to recolonize the once great planet. As mankind's last hope, the hundred adolescents will be faced with harsh conditions they'd never imagined, the secrets of their pasts, and the reality that each and every one of them needs to fight for their life.