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: 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.