100 Light Years From Home - S5-E19
Continuity mistake: At the end of the episode, Joey and Charlie are talking in the pup tent in the living room in the morning. As Charlie says, "I must have lost my touch." Joey is facing him with her hair hanging in front of her left ear and down around her face. But the next shot of Joey as she says "I don't think so"; suddenly her hair is tucked behind her left ear and away from her face. There was no movement of her hand to touch her hair in between shots.
Answer: It's only explained once in the series. Jack says to Andie "I tried to start kindergarten without you", meaning Andie was smart enough to start school early.