Parents in Park Slope say their children came home teary-eyed Monday after they say a teacher at P.S. 321 told the first graders that Santa Claus and the Tooth Fairy aren't real.

The families say it happened during a lesson about 'convincing.' They add that now they are trying to explain why the educator isn't a believer.

The principal of P.S. 231 says that this was a substitute teacher, but the moms and dads say it doesn't matter, especially that the holiday season is approaching.

In a letter sent out to parents, the principal says she was extremely upset to hear about what happened. She says they are investigating the staff member and that "...I guarantee you that this substitute will not be in class 1-216 again ... we take this very seriously."

Meanwhile, the parents say that just want their kids to understand that everyone is entitled to their own thoughts.