First of all ... to Crappie.com !!
As to your question :
A couple of things I can think of would be ... downsizing your bait, moving off the school for 15-30mins & then coming back, using my Vertical Casting method ( Crappie Pappy Article ), or vertical jigging with slight pops of the rod tip or jerking the rod tip up a foot or more or deadsticking (holding the jig as still as possible and at the same depth.
If none of those methods worked ... I'd be scouting for another spot with similar conditions.
... cp