I mean that's nice and all. But then you can also get behavioral issues from gifted students who feel stifled. Their needs aren't less important than the other students'.

Kids usually don't learn "school" things like math, reading, and science from each other. They learn behaviors. Kindness, cooperation, competition, integrity, working hard, not being disruptive etc. Having a gifted track for part of the day doesn't disrupt that learning.