NC gifted program identification criteria vary by district.
Wake County's criteria seem pretty generous. (Grade skips, dual enrollment, and other acceleration options are also available
if students show a need, so it doesn't appear that this would necessarily be detrimental to also meeting the needs of HG/PG kids.)
If these criteria for identification are typical, I wouldn't be surprised to find that better teaching methods alone could increase the proportion of students performing at or above the 90th percentile nationally on the grade-level ITBS to 15-20% of the children in the school, particularly in elementary grades.