Nicole's hair color changes from blonde to red and back to blonde. The whole movie her hair is blonde except during the hotel scene when she is outside wrapped in a blanket and tells Carlos she wants to be good for him it is red. The next shot, when they are in the car taking her back home her hair is blonde again and stays that way through the rest of the movie. The red hair was due to Kirsten Dunst starting to film Spider-Man (2002)
The blue plastic bottle is in a different position on the ground when the teacher picks it up.
Various characters' clothes change repeatedly during the first "day" of the movie.
When Maddy and Nicole drive Carlos home the first time, Nicole can be see in the back seat with Carlos before she climbs back there.
At approx. 21:10, when Maddy and Nicole are driving Carlos home, Nicole is seen jumping the back seat. In the next shot, she is back in the front before actually jumping into the back seat with Carlos.
When Maddy and Nicole drive Carlos home, Nicole's words do not match up with her mouth when she is talking to Carlos's brother.
When the bus pulls up to the school, crew (especially a boom mic operator) are reflected the bus door as it opens.
When Matty picks Nicole up for school, the cameraman's reflection is visible on the car's window.