Unless it's a gifted magnet school, any school classifying 16% of its student body as gifted is obviously mis-classifying a raftload of them. At the 84th percentile you're only just outside one standard deviation. No wonder she feels superior.
ITA and I know that I've brought up before that I feel like rampant overidentification of GT is a problem in our area. There are no gifted magnet schools locally, so this is not one. Like MON mentioned, the very large majority of kids with GT identifications do not have these ids based on IQ tests. I totally understand $ constraints for things like that, but do wish that there was a better understanding of the difference btwn a kid who is in the top 1% of ability vs. a kid who is GT b/c s/he achieves highly, was recommended by a teacher or parent using a subjective rating scale, is creative, shows evidence of leadership, or was given both the CogAT and OLSAT (sometimes more than once) and hit the 95th percentile on one part of one of these tests at least once.
Having her develop a superiority complex is definitely not desirable. Middle school was a good place for that not to be a major issue b/c, although her middle school had also identified about 17% of their kids as gifted, dd was probably the youngest in her grade with the combo of the grade skip and her bd making her younger, and she had an unusual group in that one grade where there were a few definitely gifted kids including the one friend who is HG+. While she had a lot of kids in her accelerated classes who she felt to be bozos, she had at least the few who were impressive enough that she wasn't developing a sense that she was smarter than everyone else in the school. This middle school group has dispersed & dd is at a different high school than her HG+ friend, though.
I'm not sure what more we can do to avoid dd developing an attitude problem. Like I said, some of it may be her becoming more of a teen, but it would be really nice if she could find some other kids who engage her and help ground her in the reality that the rest of the world isn't stupid. The new group with whom she is eating at lunch sounds like a better fit for her and she is signed up for speech next year, which a # of you have mentioned as a good place to meet gifted kids, so we'll see how it continues to develop.