I live in suburban midwest. I often wonder if I'm the only parent who ever emotionally left 7th grade. I've started to view these conversations as a sign of either not enough to do or not enough to think about. As time has gone by (my oldest is in 4th), the 7th grade behavior hasn't really changed, but I've gotten better at avoiding those people, and they seem to avoid me as well.
As we have a major transition coming up for DS in the school that others will noticed, I recently practiced a bunch of "buzz off" responses with a friend. For our school, conversations happen on the school corner after dropping off kids.
Use as appropriate for the situation.
"I prefer not to get into the specifics."
"Yeah, the school placed him in that class."
"Since he's so young, I haven't really worried about reading levels. I just let him read what he wants to."
"Yes, he really loves math."
"I'd love to talk to you about this, but I'm headed off to a meeting right now." (repeat daily until the person gets the drift)
(and because several kids validly need accelerations at this school:)
"Mrs. can talk to you about the procedure."
"This isn't the time or place to talk about this. I'd be happy to fill you in on things. Please just call me at work when the kids aren't listening."