The cafeteria-tribe scene, as perfected in Mean Girls, is a classic high-school-movie trope: a new kid gets a tour from a jaded expert and learns where all the different groups hang out and why they don’t mix. (Other excellent examples of such scenes can be seen in movies like 10 Things I Hate About You, below, and Clueless, among others.)
Of course, the new kid never follows the injunction not to mix cliques, which is how the plot of such a movie gets off the ground. So, in the interest of life imitating art, we would never recommend feeling bound by social norms. But we do commend the character who gives that tour, who is so hyper-aware of friend groups. He or she allows the genre to exist—so, if you see a new kid, be nice, because that crucial character could be you.