I suspect what is happening here is that while the gifted kids at the upper levels of ability
in the class are pulled out, the group of kids left in the mixed-ability class is taught at a pace/level that the lower ability kids are able to keep up with. There is a continuum of abilities in any one given mixed-ability classroom, and while we're here parenting kids at the upper upper end, there are also a lot of kids (at least in my district) who are in-between low average and not-quite-across-the-borderline-gifted who are also sitting in mixed-ability classrooms not being taught to their ability level. As a parent, I want my children to be able to work at an appropriate level of challenge, whether or not my child is PG, HG, MG or not-at-all-G but still quite capable of learning more than is being taught.
One of the reasons I have heard from the school district for having mixed-ability classes is that by exposing those students who are not identified as gifted to the same material as gifted children, it brings up their level of learning even if it is not to the level of gifted. They are examining gifted education programs not only as to how it affects the gifted child, but the non-gifted child as well.
A few reasons I have heard from at least one parent whose child is NOT in the gifted programs is that 1) her DD has more classes with children who may have behavioral issues which disrupts the class and her learning 2) her child may not feel she can take the higher-level classes in high school because she is not in the gifted classes in middle school 3) the pace is slower because the level to which they are teaching is lower since the higher-ability children are not in the classroom.
