First, although I seriously doubt an NA beer will do any harm to the kids, the teacher should have known better than to give a controlled substance to minors.
"Let's see, I need to have a drivers license and prove that I am over 21 to buy this Odoull's, but it's probably ok to just let my kids sample it in class..."
Again, I am not arguing that the "beer" would cause any ill effects, but this guy needs to let the kids' parents decide if and when the kids get to drink alcohol.