When 19th century books talk of Sunday School, it doesn't always mean children. This is kind of a youth ministry with their different teachers - some who are godly and want to lead young men and women to the Lord, and some who are worldly and have not been saved themselves. Just like today, only those young men and women still attended Bible studies and even prayer meetings, and weren't pulled to church only by seeker sensitive types of games and fun.
Great to be encouraged in your christian walk and work through these characters and to rejoice about the fruit of their labor. Let's pray for our ministries, work, but leave results to the Lord!