Why even have signs and signals? Just let the coach call them out and the opposing players can be on the "honor system" and not react to their advantage...COME ON!! If a catcher signals so low that people sitting behind him can see them, he should have them stolen. What if the catcher keeps his left leg open and the third base coach can see the signal? Honor system again? Why have multiple signals when a runner is on second? He won't steal them because that would be dishonest.
The only way your catcher is going to learn is to do it the right way so they can't be stolen. T-Ball was a long time ago.