My daughter learned the days of the week last year by singing it to the Addams Family song. I know that it's not Halloween but that's what I would think of when she sang it. It was so cute!
Check out this
site. There are some cute ideas there.
I'll have to ask her if they are singing anything in school this year. She hasn't been signing anything but the "Pledge of Allegiance" - and until my son started at this school, I never knew there actually was a song for it.
Teachers nowadays are so clever and make up songs for everything!