Why Doesn't Holden Like School? Why Is He Failing? Is He Dumb?

In the novel, The Catcher In The Rye, by J. D. Salinger, the main character Holden Caufield does not like school. In the first few chapter of the novel, you learn that he just got kicked out of school and it seems that he does not have any directions on where he is going in life. Just by that the reader already has a sense of Holden's character, and you can see that he does not care about school too much. In the beginning of the book, he says that he has bee in many different private schools before going to Pencey Prep. From what I have been reading thus far, it doesnt seem that Holden is dumb just because he got kicked out of school. But it doesnt seem that Holden doesnt care about school, or else he wouldn't be failing almost every subject.