Holden Caulfield is a typical American teenage boy in some respects, but in other respects he cannot be considered typical. For one thing, he comes from a family with a lot of money. He belongs to the upper class of the East Coast and goes to upper-class schools (and gets kicked out of them). He gets his clothes at Brooks Brothers!!! He is typical of American teenage boys in his language. He uses some profanity and a lot of hyperbole. He tries to sound more sophisticated and cynical than he really is. Like a lot of American teenage boys he hates school and is not overly fond of most teachers. He is suffering from teenage growing pains. On the other hand, he is obviously exceptionally intelligent. He probably has an IQ of around 150. He is an earlier example of the super-intelligent young people Salinger would write about a little later, including Seymour Glass, who committed suicide in the story "A Perfect Day for Bananafish." There are quite a few children in the Glass family, and all have genius intelligences, including Franny and Zooey, who had their own stories published in the New Yorker and later in book form in Franny and Zooey.
A high IQ can be an asset as well as a handicap. As a handicap it makes people seem freakish to more "average normal" people. It also tends to make the highly intelligent person despise "average normal" people to a greater or lesser degree as a sort of retaliation. Holden seems to be an introvert who is trying very hard to fit into a world dominated by extraverts. He resembles the narrator of Dostoyevsky's Notes from Underground, a man who despises most people and their values and conversations, and yet tries to get accepted by them. Holden's biggest problems, and his biggest differences from the average normal male teenagers, are that he is an introvert with a genius intelligence. Being an introvert makes him feel terribly lonely, and he doesn't realize he is a genius; in fact, he keeps saying he is dumb. He probably thinks he is dumb because he can't concentrate and keeps flunking classes. At least two of his teachers recognize that he is an ugly duckling who might turn into a swan someday.