The parents should know. The parents need to be involved in the education of their children, including (and especially) sex ed. Now whether it's the job of the school to let them know, that's debatable, but I think that if what student's classmates and/or teachers observe, his parents should know most or all of the facts about it.
Another point I'd like to bring up is that gays are not the same as Jews. The Jews were being persecuted because of merely their heritage and where they came from, not of any action of theirs. The reason it seems that gays are persecuted is because they ARE doing something wrong. The Bible literally calls homosexuality an abomination (not homosexuals, just the acts they commit). It is wrong. And don't say that they're born that way, it has to do with upbringing and the parental roles being filled properly. Nobody is born gay. Don't call lawmakers Nazis just because they try to outlaw or hinder certain types of lifestyles. They outlaw the type of murderous, thieving, and raping lifestyles that would destroy society if left unchecked, yet nobody complains except the murderers, thieves, and rapists.