The early/late arrival problem has beleaguered many programs. Sunday Schools after worship tend to avoid this problem. In-between a little less.  Early Sunday Schools BEFORE worship, however, never seem to solve people's arrival issues, rather, they adapt their program around it.

There are simple solutions, such as those mentioned and sure to come: crafts, games, etc. But there is a "structural solution" described below, that has some additional benefits.

One of the more successful workarounds to the early/late arrival problem is the "Assembly Time Before Sunday School."  Assembly is a scheduled gathering led by one or more persons, with elements of worship, music, and "introducing the story" in some creative way (sometimes a skit, or lesson game, quiz/recap of last week's lesson, 'extra' subjects like prayer/worship/mission, or short video, for example).  

The Assembly takes away some of the class' time. For example: If Sunday School CLASS usually starts at 9 am and runs until 9:50, then Assembly gets 9 to 9:15.  

As a teacher, if you want me to give up that much of my lesson, you need to make sure that Assembly "intros" what we're studying that Sunday, --otherwise, you're just cutting short Sunday School, and that's not great for creative lessons.  

Rotation churches, thus, find it EASIER to add Assembly Time to the schedule because all the classes are focusing on the same subject that day.  In fact, in the early days of Rotation, many of us thought Assembly Time should have been a REGULAR FEATURE of the WoRM, but because of facility and schedule issues, not all of us were able to do it. I liked it because it gave us a place to add music every week, but alas, the church's Sunday morning schedule and room availability didn't permit us to regularly do it.

Assembly Time allows late arrivers to be on time for AT LEAST the class AND front-loads the class with something attractive ---so many late-arrivers won't want to MISS IT.  

Hope this helps.

Neil