Continuity mistake: When Mary's grandma is teaching her to dance, Mary falls and breaks the table, but later when it flashes back the table is fixed then it's broken again.
Other mistake: In the 'sped' class the teacher starts taking attendance. He goes through and finishes but he never calls the main girl's name or her friend.
Continuity mistake: When Mary and her friend are outside of the school when the poster is being hung up, the girl is spinning a basketball on her finger - you can see a metal rod spinning for her when she moves.
Continuity mistake: When God comes to talk to Mary and she is lying in bed, she throws her covers down. When it shows Mary up close, she is holding her covers up, and in the next shot her covers are down again.
Continuity mistake: In the talent show scenes, Mary and her red-headed friend are shown several times backstage. The friend's outfit switches back and forth between her "weight-lifter" costume, which she wore for her own number, and the back-up dancer costume she wears for Mary's number.
Continuity mistake: Mary prays 3 times before bed throughout the movie. If you look, the 1st and 3rd times are the same. She's wearing the same clothes and says the same things.
Continuity mistake: When we first see Mary in the special ed class, the priest is teaching them about how the earth revolves around the sun. However, then he starts taking roll call. Wouldn't he have already done that before he started teaching the class, rather than in the middle?
Continuity mistake: When Mary is performing in the talent show tryouts, it shows her with white panties, but when she comes off the stage covered in paint, she has red panties. After she gets to the swimming pool with Slater she has white panties again. (00:50:40 - 00:52:00)
Continuity mistake: After the pool scene in the middle of the movie, Slater takes Mary home. Amazingly, her clothes are all dry and her hair is not only dry but perfectly curled and styled.
Continuity mistake: In Mary's bedroom, throughout the movie the night table and the picture on it switch from one side of the bed to the other.
Continuity mistake: In the beginning of the movie when Mary is at the pool, she is running to jump in the water, she has her flip flops on in one shot. But the next shot, just before she jumps in, she doesn't have her flip flops on.
Other mistake: After Mary has a tin of paint tipped over her head she runs out of the school, gets on the back of Slater's motorcycle, and they ride to the pool. Mary is covered in wet paint yet none of that paint is transferred to Slater's jacket. The back of the jacket is shown clean.