First off, I hope I'm understanding you correctly, in that you are trying to catch CRAPPIE around schools of Shad (& not actually trying to catch the SHAD).
Always fish under the Shad schools, rather than "in the middle of the Shad". Also, fish out around the outer perimeter area of the Shad school, but still deeper than the main body of the school. Crappie aren't going to be slashing & dashing into the school ... they're gonna pick off strays, the injured, or stragglers. If using jigs, match the size or go slightly smaller, and imitate a injured or dying Shad (drop/lift, or shaking the rod tip when letting the jig swing back to you, &/or using a lighter weight jighead for a slower fall).
If there's any cover nearby, like a standing tree or brushpile, search around that ... the Crappie know what the Shad are going to do, given the circumstances, so they'll set up in ambush spots & wait for the Shad to wander by. Shade is a big deal to Crappie, as it hides them and it's generally cooler. Depth creates shade, too ... if there's no other object around to cast a shadow.
On the other hand, everytime I've ever seen schools of Shad just tightly circling around & around in one spot ... I've never done any good. But, when the Shad are on the move, the fish seem to know ... and they set up where they expect the Shad to pass by, or follow behind the school, never getting too far away to lose contact.
... cp