I've actually been a little disappointed by my Congo Tetras lack of schooling. After a lot of reading, I was expecting schooling behavior and got 12 small juveniles from my LFS. They really only schooled until they settled into my planted tank. Now, they're scattered throughout the open areas, and only "get together" as a school when one gets a notion to dash the length of the tank, and the others fall into formation and follow. This only lasts a few seconds, and then they disband. There has also been a lot of spawning behavior, with males purposely segragating a heavy female away from the others.
My pygmy cory cats are WAY better schoolers, LOL!
I also have red-line rasboras that stay in a group, and I would rate them as moderate in schooling behavior. They don't stray far from the group, but they don't do a lot of swimming in unison which seems to be the desire of this thread.
And in yet another tank, a group of Gold Ring Danios (have not been able to identify them, I've tried) is so constantly in a busy cluster that I can't tell if there is much schooling behavior or not. I swear they know if I even look towards their tank, and group at the customary feeding area in a mad rush. I would have to say they don't have any real schooling tendency, except on occasion if they're startled.
-Jane | 
Hybrid Mode
