Kannapolis: I do not know specifically why the grades are split that way, but it is not unusual to break out grades based on space needs and to better serve the students based on different levels of maturity (9th grade centers are another example, as are K-2 and 3-6 schools), I have only briefly been in the high school for Kannapolis, but not any of their other schools. It felt more urban to me than most Cabarrus County schools (Concord). The staff I have met were all young, energetic and very happy with their jobs. That is always a good sign. The school system received a large technology donation, which is exciting:
Kannapolis City Schools, Kannapolis, NC
Concord: Look at the Cabarrus County School System. To be closer to Huntersville, you would be looking at the west side of 85, which would be Harris Road Middle and NW Cabarrus Middle, both excellent schools. Demographically, these schools are considered to be more rural. Harris is one of the largest middle schools in the state, in part because a new middle school will not open in time to ease crowding.
In all cases, middle school is arranged into teams, where the same group of students share 4 core teachers (mathematics, science, social students, english language arts). Their classes and lockers are all in the same area. Movement between classes and common areas, such as gym and the cafeteria, are times to minimize how often the different grades come together. It is for crowd and noise control. But it is also reassuring to 6th graders to not have to force their way through a bunch of 8th graders.
Middle school teachers have a special understanding of this age. Odds are, no matter which school she goes to, they will help with the transistion.