At around midday Monday at High Tech High School in North Bergen, N.J., about 40 students are crammed into a small classroom, anxiously waiting for Kendrick Lamar to walk into the room. He glides in with crisp white kicks, a grey long-sleeve shirt, and hair twisting every which way. The 27-year-old rapper has a broad smile on his face. He seems almost as excited as the students, who just might be having their best day of school ... ever.