I strayed from Sunday school for many years. I was told that the Sunday school era was over. It confined people to a certain hour on a certain day; growth would be limited by the size of building, etc.
Small groups were the thing. The unlimited space and scheduling options promised the potential for megachurch results. There were rumors of super churches in Korea and other far away places. Furthermore, this model was used successfully by AA, Campus Crusade and other parachurch groups.
As a church planter (usually lacking buildings) this was good news. I read all the books I could find, I went to a few training events and I diligently started small groups that multiplied. I even used home-based small groups when I had church buildings.
I had as much success as anyone in my corner of the world but I was growing weary of stagnant groups, absenteeism (work, school, sick, etc.), and childcare issues. I noticed that our local megachurch was doing things a little different. Their groups met on Wednesday, Thursday and Friday at the church. This not only provided a consistent and familiar location but also childcare. AND they were showing remarkable growth.
I took this to be a revelation and moved our small groups to Sunday morning. People were already there for worship and there was childcare available. The results were immediate: reduced stress, increased attendance and new members.
I believe that small groups are essential to a healthy, growing church and can be done just as easily (perhaps, easier) on Sunday morning as they are on any other day and time. On Sunday you have the advantage of mutual supporting activities. This doesn’t rule out other small groups but Sunday school is far from dead.
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