Everything Put Together Falls Apart - S6-E9
Plot hole: When Pacey first finds Emma in the bathroom cleaning the toilet, she makes a point of mentioning that 'she has band practice in an hour'. But right after they 'strike a deal' and Pacey agrees to her terms for the party, Emma suddenly announces that 'she is off to band practice'. Only a few minutes have passed, so it seems strange Emma would suddenly be going to a band practice that doesn't actually start for another hour.
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.