Teddy Roosevelt said that nothing in the world is worth doing unless it meant effort, pain and difficulty -- and no, he wasn't talking about teaching your teen to drive. Notice, too, he never mentioned you need to have an audience. In fact, teen drivers are generally safer on the road when they fly solo rather than with friends -- peers as passengers can turn a drive from school to home into a social event.
To the point: Teen drivers aged 15 to 17 with two or more peer passengers in their cars have a nearly eight-fold increased risk of having a fatal accident than when they drive alone. It's not (just) showing off, though; during adolescence the brain hasn't yet fully developed to weigh the consequences of risk taking, and teens may not be as good at identifying and evaluating dangerous situations and other hazards while driving.
Studies find when teenage drivers have teenage passengers they engage in more risky driving behaviors such as speeding (more than 15 mph -- 24 kph -- over the speed limit), swerving, straying from their lane or across the center line, running a red light, and maintaining unsafe, shorter following distances [sources: Halsey, Winston]. As many as 71 percent of male teen drivers and just shy of half of female teen drivers admit they get distracted by their friends in the car. And studies show those answers are truthful: Male teen drivers with teenage passengers, for example, are twice as likely to engage in aggressive driving and are nearly six times more likely to pull off a dangerous driving maneuver than when they drive alone [source: Curry].