Stable, reasonable drive from the northwest side of Atlanta, and have a track record to show that they can get a kid to college gymnastics I would say are GAA (great facility, not sure if they are getting rid of their elite program or not; but if you are wanting college that won't matter and GAA can definitely get kids to college gymnastics), GA Allstars (they are going through an ownership change; but I have heard great things about the coaches who are taking over ownership, they have been coaching there for years), Northwind, Paulding (only recently started getting kids to college gymnastics; but a great program and they have been placing really high. The owner is a great guy), NorthStars (Whitney's old gym), Cartersville (generally a very solid team for girls and boys), and Roswell (very large team, generally does really well, great facility).
Don't count these gyms out though - Cobb (HC is a great guy, great facility, gym does focus a bit more on the boys' team than most gyms. They are going through some coaching changes that could be good or bad, verdict is out), World of Gymnastics (they were kind of out of the scene for a bit; but have been coming back in the past couple of years and have been doing well), Integra (new gym, only competed for 3 seasons), North Metro (going through some coaching changes, have lost a lot of girls; but still have some great coaches).
Then you have on the other side of Atlanta, NorthEast. There you have Ultimate (generally do really well, have some new coaches), Top Notch (have girls going for elite, not sure if they have any yet), Atlanta School of Gymnastics (generally very solid, you have ASG Lawrenceville and ASG Tucker), Gymnastix (owners big in USAG for GA).
There are a lot of other gyms around that are smaller or I might just be forgetting.
There is also Ga Elite that has been mentioned in the thread; but that is near Athens. I can not imagine driving over there for gymnastics without moving closer (especially closer than the Marietta/Kennesaw/Roswell area - that would be around 90 miles each way! And as someone else already mentioned, it can take 30 minutes or more to go 10 miles).
School wise, generally Cobb and parts of Cherokee are considered great school systems. I'd avoid City of Atlanta schools for the most part. With Cobb and Cherokee you would want to check the specific schools because while in general the schools are great, there are some that have issues. In Cobb you also have City of Marietta schools, much smaller school system with only one high school (Cobb has 16 high schools, of those at least 5 tend to be nationally ranked schools. Many of the high schools have magnet programs. Cherokee has 7 high schools, in general is a smaller school system, which has its plusses). Gwinett also has some good schools. The key to all of these is to research the schools, visit them, be sure before you buy a house in an area. The zoned schools really make a difference in the home value, so it could be easy to get tempted to buy some AWESOME home only to then find out that it was so affordable because the schools aren't very good.
If sticking more to the NorthWest side, traffic can be a real issue. Roswell/Alpharetta have IMO HORRIBLE traffic. You do have easy access to interstates; but there is traffic on those too. East Cobb is maybe a bit better than Roswell/Alpharetta; but not by much. Cherokee is a little better for traffic; but if you work in actual Atlanta the traffic to get to/from work would be horrific. West Cobb has better traffic in general; but isn't right on any interstate and there is a lot of growth there right now, so traffic is probably to get much worse.