My current go-to answer is: "Because DD was reading to the class for story time in pre-K. She didn't have anything to learn in kindergarten, so we skipped her." It's an easily-digested reason which has the benefit of being true, though it lacks nuance and skips over a whole lot of strife between K and skip.
DD is large-ish for her age and in an age-sorted soccer league, so it's important for us to be able to explain that, although she's in 5th grade, that doesn't mean we're cheating the system, she really does belong on a U10 team. There are three other kids on her team who go to her school, and two have been in gifted classes with her, so there's no keeping it a secret.
