"Kids never pay attention to the substitutes."
They rarely pay attention to much in public schools. Check thenational public school reading and math scores against homeschoolers lately?
Less paying attention to their teachers would tend to raise those scores, IMO.
My 9-year-old's teacher didn't have a problem with Santa Claus, but when it came time to teach multiplication she taught them about the Tin Man and the Magic Zero. I sat in on a lesson because my normally bright child was having so much trouble learning multiplication and when we worked together at home he was thoroughly confused.
After hearing what his teacher was teaching him, the Tin Man and the Magic Zero crap, I told him to just forget it all and I'd teach him. Now he's got it. ;-)
People are free to believe what they want. And if there is a family out there who believes that Santa Claus is god, it is not up to a substitute teacher to decide to tell children he's not. Read the poem, draw the check for filling in for a day and keep your beliefs to yourself.
How is this different from an atheist substitute teacher announcing to the kids that God isn't real and Jesus didn't rise from the dead? After all, that's what an atheist substitue would believe.