As suggested above, Catcher in the Rye is often taught in 10th grade classes.
There is a relatively small number of cannonical texts available for the 10th grade level compared to the 11th and 12th grade levels. This does not argue for the appropriateness or aptness of the text for 10th graders adn doesn't argue against any aptness for 11th adn 12th grades.
Probably, some of the deeper issues and the greatest wealth of the artistic statement of the novel is lost on many 10th graders and would be better received by people a few steps closer to the big decisions of adulthood.
I think in terms of acceptable content this book is actually very tame compared to other books that are widely taught with far more objectionable content. Just take Hunger Games, for example, or The Chocolate War. If I was going to teach this book in terms of academic level, however, I would want to teach it at Grade 11 and Grade 12 level.
I actually just taught The Catcher in the Rye in my tenth grade class (it's one of four required texts for this grade level in my school district). So I think that the read would be appropriate for grade 11 and/or 12 students in terms of ability. But other factors certainly go into choosing books that are "appropriate"--consider the climate of your district and community and compare the novel to others on the current reading list.
I read Catcher in the ninth grade and many of my former students read it as freshmen too. It was one of literally four books I enjoyed reading in high school (others were Lord of the Flies, All Quiet on the Western Front and A Separate Peace). I think that the reason it is so widely assigned is because it is an easy draw for students. Teens love to read about other teens rebelling, teens whose plight is worse than their own and teens who experience the same confusion they do. I think the most successfully assigned novels are those to which students can relate. The story is high-interest and easy to read. There is very little difficult vocabulary and the protagonist is endearing. Not everything students read needs to be Shakespeare.
I have heard the criticism of post four quite often. For my bet, I am not sure where I stand. I do believe it is a good book and there are moments of greatness within it. Yet, over time, I have become a bit more open to the idea that there are more worthy and relevant books that can generate the same types of discussions that arise from The Catcher in the Rye. If we are talking about individual vs. society, why not Beloved, where slavery and discrimination permanently alters a woman and its legacy taints her actions and the relationship between her child and sense of self? If we are examining the idea of the bildungsroman, why not Joyce's Portrait of the Artist or Tan's The Joy Luck Club? (The latter would be a challenging read for 11th and 12th grade, but if they undertook it, the discussions would be so broad and open that its rewards speak for themselves.) The list is quite vast of quality literature that can be appreciated by Juniors and Seniors in High School. Catcher in the Rye is appropriate for this level, but perhaps the discussion might need to be broadened.
I'm probably the only person in the universe who thinks this, but I've never considered The Catcher in the Rye to be a particularly good book. I don't think it's very well-written, and I honestly believe that all the controversy about it (the language and subject matter) is what propelled it to being considered a "classic" - if people had ignored it back when it was first published, I don't think it would even be taught or read very much anymore.
I think with all of the great works of literature out there, this is a pretty poor choice to add to any high school reading list, regardless of grade level or age of students.
I teach this book as part of a unit with my juniors. They have the choice of Bean Trees, Catcher in the Rye or Brave New World. For my students, this works even with the prostitution and profanity because we've read other works with controversal language. When we read Of Mice and Men, we look at who swears and when they swear and how this affects our interpretation of the characters. When we read "The Adventure of the German Student" (Irving) and "Cask of Amontillado" (Poe), we talk about the sexual subtext. So, by the time the students reach the end of the year with either Catcher or Brave New World, I've modelled good reading habits with them, focusing them on the thematic meanings and discouraging the more salacious comments, usually by ignoring them or telling the students to show more maturity.
So, if you're planning on being a teacher, my advice would be to slowly increase the controversy of the material you present to students. If you do this, I think Catcher is very appropriate. My students who read it still identify with the hopelessness and frustration (even though I think it's a bit dated), and many name the book as one of their favorites.
I am a high school teacher and we use this book in English 11. But I would think that it is appropriate for Grade 12 as well. It is a coming of age story about a boy who is in high school. It is widely read in Junior year in my area in New York
I'm rereading Catcher in the Rye and remember it quite fondly from my original reading at around 15 years of age. Since my daughter is going into 10th Grade, I'm puzzled about why it is just being considered for 11th and 12th Grades. It had a taste of 'forbidden fruit' for me, but that was forty years ago! As jlcannad says, it is dated. I believe that it still 'strikes home' however, and both I and my daughter identify with Holden! I disagree with akannan insofar as he mentions other books which are 'more worthy and relevant'. Joyce's Portrait of the Artist would be a possible additional work, although I think much of Joyce's other work, to which students usually refer while studying a particular text, would be too complex for them at this point and would prevent true appreciation. I believe Catcher should be retained because it represents American literature (increasingly difficult to find being studied in American schools these days!) while Beloved is an African American work and The Joy Luck Club is Asian American. I believe we need to hold on to such works as Catcher to prevent non-minority students being made to feel guilty about their heritage, or certainly being made to feel that works such as Catcher lack the merit of those depicting the struggles of minority groups. This is actually a form of reverse discrimination.