mark twain does not tell what happens at the end oh ch 4 why does twain not explain the scene

The Judge asks Tom to name the 12 apostles and the only thing he can come up with is David and Goliath. The narrator (Mr Twain) decides he's humiliated Tom enough and moves on......... he doesn't need to explain. Most every child or adult in Twain's day would have recognized Tom's mistake immediately.