Run track because you get two benefits. First, you add a sport to your resume, run your Junior year and you can run your Senior year so you have two years of a sport. Secondly, it will make you a better runner and teach you how to train for a run as well as make you run a distance if you pick the right event.
My DS was a rugby player so he was not thin. He joined the track team and told the coach he wanted to run the mile to help him train for the CFA. The coach knew my DS was not going to bring home any trophies, but one more kid running on the road didn't hurt. My DS ran the mile and finished last or second last in every race. It was pretty funny seeing him standing next to all the other tall, skinny runners. But, he got his mile time down to 6:11 in competition, taught him how to train for running, and gave him confidence for long runs since practice sometimes included a 5 to 7 mile run. He ran a 6:08 for the CFA so he was pleased. He was lucky that his teammates were totally behind him though. It would have been easy to leave him in the dust, but they were great teammates and gave him tips, ran with him at times and just overall supported his efforts.
This is one of the reasons the academies like team sports participation. You learn that teammates support one another and the impact that the support can have. Makes you a better teammate, leader and follower.