I have to say that my own personal experience, in the classroom, is limited in regards to "gifted" students. While I have some students who "get it," many in the district I teach in are simply happy to pass. Outside of that, my own children are both in advanced placement classes for English and Math. I feel like this atmosphere allows the students to negotiate the material on a more similar level than classrooms in which contain all levels of students.
As an example, I would point out the special education classrooms which teach to lower-level and lower functioning students. They are not in general education classes for a reason (meaning the focus is on the level of the students to which the teacher teaches). This alone is an example of why advanced, or gifted, students need a classroom of their own.