A darling idea for teaching this theme can be found here. Why reinvent the wheel??? A PDF for a piggy bank is provided but if you do not want to make it, you can always use a real one. Assign songs for practice to 9 quarters. Invite a child to drop a quarter into the bank & then sing the corresponding song. Keep the tenth quarter out so you can talk about giving the Lord one tenth (put in a tithing envelope). Bear your testimony of the blessings that are received from paying a full tithe. Have fun!