While most teens hit the beach each summer, high school senior Brandon Martin is up to his elbows in ochre and watermelon as an employee of Seeds for Learning-Beyond the Farm, a program that helps Philadelphia high schoolers plant their own urban gardens and learn about nutrition and business. Martin, who wants to become a chef, doesn’t plan to come out of the garden anytime soon. Knowledge@Wharton High School talked to Martin when he was a sophomore about his summer experience and more.…