People usually form groups based on interests, hobbies, likes and dislikes, sports activities, etc. This is how cliques form. For example, in high school many cliques are organized by popularity. There have always been cliques but the truth is that once high school is over people go their separate ways.
Self esteem is almost always an issue, even for the so called "popular" kids. Cliques form as a way to validate peoples' self worth. Cliques include some, which feels very rewarding - you are worthy of being included in the group, and exclude others, which the clique can then make fun of or enjoy excluding. This validates a "we're better than you" attitude. Cliques fade away and break apart when school ends and people grow older and mature.
In my mind, the fundamental reason the cliques exist is the developmental need to be able to associate with others and to simply "belong." It seems to be an on face contradiction in which high school students cling to their freedom and sense of autonomy. Yet, this spirit of independence seems to drive them to social groupings or cliques where they sacrifice their spirit of independence in order to belong. The need to possess some level of social identity is of critical importance to all students, but seems to be more pressing to the high school student. Part of this might be due to the fact that students are feeling older and more mature than at any other point in their lives and to replicate what they perceive "adults do" could compel them to embrace a lifestyle based on cliques and social groupings.
Take a look at your experiences since kindergarten.
In Kindergarten, 1st and 2nd grade, anyone can really play with anyone on a given day. In fact, boys and girls can be friends with each other and no one really makes comments. Kids of different races can be friends and no one makes comments. There aren't cliques really yet... and if there are, they are usually influenced by parents...
Changes occur throughout the grades 3-8. LOTS of them. Kids say mean things and suddenly, it doesn't just roll off your back anymore, you begin to take some things personally. Your brain is developing even further and throughout puberty, you are especially sensitive. You get to a point at which you just don't want to hurt.
I think by high school students enter cliques for safety. The premise of Anderson's Speak hinges on this thought. The main character was hurt between her 8th grade and freshmen years and is now dealing with that internally. Teenagers long for acceptance because they hope that if they are accepted by the group, no one will hurt them.
Your teacher is doing you a favor by assigning this book... take full advantage of it.
In my opinion, there are a couple of reasons for this.
One is that high school is a time in your life (more than most others) when you are forced to spend most of your day around a wide variety of kinds of people. When you hang out with people "like you" in high school, it's called a clique. Later on, you'll hang out with people like you, but there won't be the other kinds of people around so it won't seem like a clique -- you'll just always be with "your kind."
The other thing is that teens, in my opinion, see the world more in black and white than in shades of gray. People are either good or bad, cool or not. So people who think the same want to hang out together and they dislike the other kinds of people more than they would later in life. Later in life, it's easier to to be more tolerant of differences, I think.
In my opinion by the time you get to high school you've figured out, to some extent, what your personality is and what personalities clash with your own plus you've already made friends prior to high school.
People tend to associate by resemblances and common interests in order to protect those aspects of the group and its individuals.
i got 10 points!