Twenty years ago, I taught Sunday School for fifth graders in a mainline church. I was appalled at the lack of knowledge the kids had. For four years, I followed the curriculum but in the fifth year, I decided that along with the curriculum, I would require the kids to learn by heart just one thing...the Lord's Prayer. We recited the prayer at the beginning of class for each week. After six weeks I informed the class that they would be getting a test on the Lord's Prayer the following week. They complained bitterly and said I had no right to do that because, after all, SS was not "school."
Nevertheless, I gave them the test. I printed out the prayer and put in blanks for just ten words. Only 20% of the students were able to achieve a passing grade of 70%. The rest were only able to fill in 50% or less of the blanks.
After that, I was told by the church administration that the purpose of SS was to entertain, not teach.