Maybe the principal's worried that...if you tell the kids you're pregnant they'll ask where babies come from and then you'll have to have a covo about SEX. lol
I don't know much about 5th graders...how old are they? Are they young enough that they don't know about reproduction? Do they take like...kiddie biology? *clueless*
But yeah, maybe some parents would be ticked because they're not ready to have the "baby talk" with their kids.