The curriculum has them learning Bible stories and doing crafts. It focuses on various themes. Right now it's on belonging to God. They see how this is played out in the various Bible stories.
They also manage, even with just three of them, to rarely work without bumping and nudging and interacting with one another. We'll call that Practicing Christian Community. :-)
I also have to put a plug in for the picture Bible Sam received from his Aunt and Uncle (and cousin?) for Christmas. (Someone at church calls it the "Prince Valiant Bible" for its artistic style.) We are up to Judges and he loves it. The thing I really appreciate is the care the editor took in straightening out issues which might otherwise seem nonsensical or contradictory or cruel.
The editor will have a severe test in Judges, though, with the dismembering of the prostitute.
Back to Sunday school: If you are reading this (and you must be), what are your best and worst memories from Sunday school when growing up?