Thank you all for your responses. It's very helpful to get your perspectives.

Do you all think that our kids (or some HG kids) don't realize they are acting out because of being bored and frustrated that they aren't learning anything? I've asked my son several times in different ways why his behavior has changed at school. He never has an answer for me. However, at other times when we aren't talking about his behavior, he complains endlessly about not learning anything, being bored, etc. So do you think he's not capable of linking his behavior to the boredom and frustration?

HowlerKarma, I don't think it's SAD because while it has started in January each year for the last three years, it actually gets worse as the school year progresses. I almost pulled him out of school six weeks before the end of the last school year because it got so bad. We definitely cannot repeat that again this year!