There Is No Darkness(1983)

Joe Haldeman

Carl Bok is a citizen of Springworld, the heavy-gravity planet with monstrous and dangerous flora and fauna. Carl is well over two metres tall and weighs-in at 180 kilograms. Now Carl has won a scholarship to Starschool. He'll spend a year on this touring school, visiting sixteen of the colonized planets. This will be the experience of a lifetime.

It's tough enough for Carl as the poor scholarship student among the rich kids. His problems get worse when they arrive at Earth. Carl finds himself in urgent need of big money and, since he's a pretty tough guy, becomes a paid fighter. He has to fight dangerous and deadly human and animal opponents. His fellow students, B'oosa, Miko, Alegria and Francisco "Pancho" Bolivar, get caught up in his exploits. And then there are the aliens.