You must teach what is in accord with sound doctrine.
When we were taught the "Lord's Prayer" or "The Ten Commandments" or even "The Apostle's Creed," in Sunday School, they weren't taught to us for us to just memorize and not apply them. These beliefs that we recite are the law and provide discipline to our daily lives. Now that we are adults, we must apply God's law and stick to it to create a barrier that the enemy cannot penetrate. Sticking to sound doctrine leads to a well disciplined lifestyle.