As for other matters, brothers and sisters, we instructed you how to live in order to please God, as in fact you are living. Now we ask you and urge you in the Lord Jesus to do this more and more.
1 Thessalonians 4:1
Sunday School classes teaches us how to live our life, comforts us in our times of need, helps us to know who God is, and gives us some incite on our future on earth and with God.