smiley face stamps at school

A father is upset that his son came home from school with a smiley face stamp on the back of his hand.  The words "I need lunch money" was under the face.  He claims that this is a form of bullying and shaming kids who don't have any money.  The school sees it differently though.  The Principal says that the stamp isn't the first request for owed lunch money.  And if a parent doesn't want their kid "stamped," they can ask the school to refrain from doing it.  
My job at a local elementary school is Nutrition Secretary...I'm the one in charge of that stamp.  I hate giving it to the kids but some of them ask for it.  I prefer to let the school handle the money details with the parents because I don't think kids should have to worry about things like that.  
Was this dad right?  school stamp