All Good Things... (1) - S6-E23
Continuity mistake: When Joey and Pacey are standing in his restaurant, watching Dawson and the others come there is a shot of Joey with her hair tucked behind her right ear. But in the next shot of her, a close-up, she suddenly has all her hair pulled forward around her face. Her arms haven't moved between shots. (00:23:15)
All Good Things... (1) - S6-E23
Continuity mistake: When Joey is kissing Chris at the start, at first her hand is down, resting on the cushion. When the shot changes (right before she asks 'I don't really sound like her, do I?') her hand is up on the back of his neck. (00:03:05)
All Good Things... (1) - S6-E23
Continuity mistake: When Jack is pulled over near the start the creek behind him is empty, and remains like that throughout the scene. Then for the last few shots before he drives off again a sailboat has appeared in the background, literally out of nowhere. (00:06:45)
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.