I draw on specifics (as you may have noticed). In my daughter’s case, part of her acceleration in mathematics was based on a conscious decision that she made at the 7th grade level–and not of the category that you might think. She was in the group that ucbalumnus would call one year ahead. The school did not accelerate beyond that. So, taking 8th-grade honors math in 7th grade, she found herself in a class that was 80% male. So far, fine. However, 7th grade boys are not particularly mature, and a few of the other students were below the normal maturity level of 7th grade boys. The teacher was often elsewhere when the students entered the classroom. A few of the boys frequently made crude remarks (extending to explicitly mentioning rape–I am editing this to indicate that no one was actually raped!) before the teacher came in. The girls took to hiding out in the teacher’s office until the teacher got there. It was just a few minutes, but it was enough to create a decidedly hostile environment for the girls. My daughter decided that not only did she like math quite a lot, but she also thought that she could qualify for acceleration at the local university that the more troublesome boys could not qualify for. With some trepidation, my spouse and I agreed to that. Of course, this explanation of her acceleration did not go into any of the application materials. It might have looked like a case of pushy parents, or a student just hoping for admissions advantage; but it was something very different, unpredictable and undetectable to admissions. She was admitted to 7 of the 8 places where she applied, and chose a great fit from among those. (But one wonders from time to time about the big fish that got away.)