It depends on the age of the kids, but in the days when I was involved with kids in the 10-12 age bracket, we often enlisted the help of the kids in making activities for other children. Some of the ones that I remember most clearly were quizzes, and miming. Seeing I was a science teacher back in those days I used to run a science segment which would either provide an interesting lesson, or help the kids to understand something really important. That used to be very popular – particularly when I produced explosions! Then once a year the kids would take all the preliminaries for the church service. That would take quite a bit of preparation getting them ready to lead out in the songs and practising special items, but it had an element of service about it so it was an important part of their training.
I think that with children, we need to think outside the box a bit. They are typically in school for 5 days a week and giving them another hour of school is really just more of the same. I like to think that Sabbath is really special and something to look forward to.
Source: Daily Sabbath School Lessons