Indeed they do. You're right, and it's a disaster.
With that said, is it possible that high-potential children could be viewed as something other than interchangeable widgets whose primary purpose is to make public schools that are failing many students look good? Especially given that such schools are often little better at meeting the needs of the high-potential children than they are all of the other children.
You're right. Charter schools are often guilty of creaming. Yet, are we doing anyone a favor by sacrificing the education of high-potential children to mask problems?