Santa/Elf true believers?

What age do you think your students stop believing in Santa and the Elf on the Shelf? I teach 4th grade, and I would say most of my student still believe in Santa.

The 5th grade teachers do an elf on the shelf, and those 10 year old 100% believe there is a magic elf in their classroom. Does that sound crazy to anyone else? Don’t you think they should have more critical thinking skills?!?