They don't really school, they're shoaling fish (there was a thread here not long ago about the difference). Basically, they don't swim around with each other in lock-step like tetras, but they will hang together in a loose group, then split apart, then regroup. And they'll usually rest together in a little bunch.
If you want to see them all together, drop in an algae wafer or shrimp pellets. They'll group around them in no time. That's how I do an occasional 'tail count' on my panda corys, since they sometimes spread out so much I only see 4 or 5 at the same time. But once that algae wafer softens up, there are six tails wagging around it like it diners at a round table.
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