First, I know it has been a while since you posted but...
"But I can tell you that my younger son, who was in the private school starting in third grade, had absolutely no connection whatsoever with Caulfield. I think too much has changed since the novel was written, too much has changed from the world Salinger is conveying, for kids today (and that son would have read Catcher a good fifteen years ago) to begin to connect with it. "
One thing that hasn't changed is adults being accurately able to understand what kids relate to.
I have no great insight into kids. I am a teacher and have a toddler... so I, like you have some insight; I could be far off here but I imagine a child's connection to Caulfield is no less likely than an adults connection to a third grader. The language has nothing to do with the theme and the language isn't what drew it to readers it was the universal theme of adolescence being misunderstood.
Next, "It's a stupid book and is simply not worth reading. It is absolutely not worth being required reading for today's students." Well, your opinion certainly makes sense to you..and you think your opinion should be some sort of universal jury. Thank goodness it isn't. I don't think any book should be required. In fact there is no book that is required reading I teacher To Kill a Mockingbird. It is part of my curriculum but it certainly isn't required anymore than driving the speed limit is. If you don't read it don't get caught and if you truly have a problem let me know. If you have a valid argument we can always work something out. However, who the hell would I be to say what is or isn't, "worth reading?" I make that determination for me... I won't read a great many books but that's an opinion that only deals with my reading list.
Lastly, about 50% of your post regarded your ability to put your kids into a private school. It occurs to me there was probably a reason for that. So, I would like to say congratulations! That is obviously something that you take pride in and I hope benefits your children.