graceful mom,
We had the same issue with DD7 when she was about 3 and had started going part time to a day care/preschool and she was the only "day care" kid doing the "prep for kindergarten" stuff and doing it better than the kids in that class.
We told her that the ages written on books and games and things were with respect to what age her brain works on, not what age her body actually is. (It was truly a moment of mommy inspiration when I came up with that one smile ) She thought about that for a minute and then must have agreed that I was right, because it wasn't until about a year ago when we started buying stuff for DD2 that was above her "body" age that DD7 remembered that and made some comment about it.