I think one of the most difficult issues I've encountered in advocacy is the unwillingness to accelerate/give more appropriate work at the kid's readiness level based on social reasons. "We are concerned about his social development, and if we push him, he will be negatively impacted." I would give them links to free Nation Deceived download, which has tons of studies showing no negative social impact in acceleration.
http://www.accelerationinstitute.org/nation_deceived/Another big issue is that teachers will sometimes think that a kid cannot be ready for higher level stuff if they can't _____ (write well enough, e.g.). We were told that our kiddo couldn't move up another year in math because he couldn't keep up with the handwriting. But then we transferred him to a school where he was given that higher level math, and the experienced teacher said it wasn't a problem if he couldn't write all the answers, he could show that he understood it in other ways (verbally, e.g.), and eventually his handwriting would catch up.
In my opinion, many GT kids will rise or sink to the social level they are placed in. After my kiddo skipped a grade, we heard more than once when talking about his handwriting issues "Oh, I forgot he skipped a grade."
So many things, but I think the best thing that we encountered was flexibility and willingness to try different things for these kids who are outside the norm.
