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While I hear words like "toxic" for gifted kids in bad environments, typically mixing in with NT kids does not result in physical harm.
Psychological harm is being discussed when a "toxic" environment is mentioned. Resources such as those found at SENG, Great Potential Press, Prufrock Press, and Magination Press - American Psychological Association (APA) are often brought to bear. Whether wounds are physical or psychological, there may be some which heal well and others which may have lingering effects.

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In the past, about half of the kids took an AP exam, and the average score was 4+. We'll see what happens.
With changes to AP, a year-over-year comparison will be apples-and-oranges at best.