I am one of the founders of a private school for gifted kids (although we didn't call it that). But, as a teacher, I returned to the public school system for precisely the reasons you have mentioned in the parts about funding. Kids whose parents are middle class or above have enough resources to get their children at least part of what they need. It is the gifted children of poor parents who often do not understand the needs of their gifted children and who frequently don't have the resources, financially, emotionally, logistically, and time-wise to help their children as much as the children need it.

And, the solutions I advocate are ones that I call "structural" - self-contained GT classes, cluster-grouping (though I am less familiar with it and thus don't know its advantages and pitfalls), and acceleration. I am not a big fan of pull-out programs, even though I ran one for 5 years. They too often turn into "fun and games for smart kids", rather than an integral part of their learning program. As you know, I am also not a big fan of differentiation, 1) because I just don't see it happening in real life. And, 2) even if it were to happen across the board, I still believe it would not be enough for highly gifted students. And 3) school districts and hiring personnel use it to pretend that all teachers can serve their gifted students and that they thus don't need GT teachers any more. Note: this doesn't work for learning disabled students, just gifted ones.