Do you mean the parents for having strange religious beliefs or the school for having their no piercing policy? The parents can have any belief they want. But I draw the line at having my daughter (or son) go into school with a nose ring.
There are a thousand little things that adults can do, to prepare a child for being an adult. And one of them is not wearing a nose ring for school or a job interview. I'll go on record as saying these parents and the ACLU are a bunch of horse-asses in this case - they're sacrificing this kid's education.