My Big Question

In school societies, students are judged not only based on the way they dress but who they speak to or hang out with inside and outside of school. With different crowds of people, some neglect certain crowds based on whats interests they have and whats on the outside on the outside when they have no clue as to who they really are. There is no harm in getting to know people who you would think to never speak to just because they're not in the "in crowd" or in your group of friends. My question is why as high school students do we judge others on hair, clothes, cars, religion, race, or reputation? It shouldn't matter what someone seems or looks like on the outside. For all we know that person could be hurting inside.