Falling Down - S4-E2
Plot hole: When Dawson goes over to Joey's house to talk to her about Pacey's school problems, he mentions that Pacey had missed that entire day of school. Joey apparently didn't know this, as she is surprised at the news. Since Joey and Pacey are closely involved - wouldn't she have noticed his absence at school that day already? Surely she would have noticed Pacey missing for an entire day of school.
Falling Down - S4-E2
Plot hole: Mrs. Valentine almost fires Joey, after discovering that she lied about knowing the Owens. Drue steps in and saves Joey's job by claiming he did see the Owen boy. But Joey keeps her job throughout the rest of that season. Since the Owens were said to be in Paris only until the 1st of the year - wouldn't Mrs. Valentine have found that Joey lied about knowing them as soon as they returned to Capeside? Surely Mrs. Valentine would have mentioned Joey to the Owens; thinking she was their good friend, and because she was new on staff at the Country Club they were members of the board for. And once she found out Joey had indeed lied, why did she not fire her at that point?
Answer: They are not twins (Jack is older than Andie). It is possible due to when birthdays fall in the school calender for non-twin siblings to end up in the same grade. Say that you have to be 5 on Sept 1 to start Kindergarten, you are born on Sept 2, 2000 and your little sister on Aug 30, 2001. Sept 1, 2005, you are 4 years and 364 days and can't start. So Sept 1, 2006, you are 5 years and 364 days and your sister is 5 years and 1 day, and, voila!, you're both in the same grade.