Players cannot choose preset or custom classes. They all start with a Skorpion and an M9.
There are sprites (yellow glows containing items) around the map which have weapons, equipment or perks that the players can pick up. Once a player picks up a weapon or perk from a sprite, it turns red, then the sprite regenerates the same weapon, perk, or equipment after a set period of time.
This game mode is much like a typical arena shooter. The name "Old School" most likely refers to earlier days of FPS games in which players had significantly more health than in CoD games, and often had to pick up weapons from the floor.