Parents who choose to hand over the education of their child to an institution should do so on the knowledge that it is 'not guaranteed nut free' - while if they dislike a specific aspect of something that has gone on at school - something non-criminal but offensive to them - then they can request that it be stopped. But pushing for, or endorsing, a suspension for an incident of someone sharing and offering to perform some physically non-harmful superstition with your child - particularly if it was a one-off, seems utter overkill.
Would some of the members here be responding the same way if the shoe was on the other foot, I wonder... If it were an atheist teacher who told a kid that they didn't believe in a deity and perhaps took it a step further by questioning the child about their reasons for believing, or whatever?

Edit: Just read XC's input at the top of this page, which has thrown some light on matters.