RITE OF PASSAGE by Alexei Panshin.
Here is the description from Amazon:
In 2198, one hundred and fifty years after the desperate wars that destroyed an overpopulated Earth, Man lives precariously on a hundred hastily-established colony worlds and in the seven giant Ships that once ferried men to the stars. Mia Havero's Ship is a small closed society. It tests its children by casting them out to live or die in a month of Trial in the hostile wilds of a colony world. Mia Havero's Trial is fast approaching and in the meantime she must learn not only the skills that will keep her alive but the deeper courage to face herself and her world. Published originally in 1968, Alexei Panshin's Nebula Award-winning classic has lost none of its relevance, with its keen exploration of societal stagnation and the resilience of youth.