Ultimately, this is my problem with the genre, and maybe it’s a personal hang-up with horror movies in general. I never feel reassured, never think “this couldn’t happen” to me. As a horror viewer, I’m too open to suggestion, too willing to go completely with the story and identify with even the most outlandish of scenarios. For me, there is never the post-horror-film release—what aficionados liken to roller coasters or even sex—I always imagine what happens after the credits roll. In slasher films, I imagine all the therapy the lone girl survivor will need; in bad seed movies I imagine the lives ruined, the hopes every parent harbors for their child dashed, the pain and guilt and loss. Which is another way of saying that I can't wait to catch up to the new Muppets movie, and I'm fine with that.
I have never cared for bad seed films and it took a parent to explain what it is I don't care for about them. Two of three categories in the genre, as Jessica Roake puts it, hinge upon the assumption that the evil child is an Aryan genetically-guided psychopath or a literal hell-spawn. Not being a parent I may not fully appreciate stories in which the horror is discovering your kid has turned out evil despite your best efforts.
The third category deals with horrific children who mirror the evils of the mother and I'm not aware of such movies because even the premises of categoris 1 and 2 seem so noxious to me they don't interest me. While research on cognitive development and neurology suggest we are not as free as we often like to think we are socialization is not completely out of the picture. There are sociopaths for whom empathy is essentially impossible but these are not usual, which is why we eventually notice them.
At another level the whole genre of the bad seed can be construed, within Christian terms, as a blunt genre examination of the anxiety that evil passes from one generation to the next in ways we can't understand, or that a person is capable of evil whether or not we would wish them to. Adam and Eve had the grand-daddy of all bad seed babies in Cain, right? And the narrative literature abounds with wicked kings who sinned as their fathers did. Or we read about people like Samson who did all kinds of stupid things despite the warnings of his parents. It "is" more common for Eli to beget corrupt sons, and yet Samuel's own sons were so venal and corrupt it was one of the reasons Israel requested a king! Thus King Saul.
King Saul was an unstable and crazy man who fathered Jonathan. There are strange cases in which, despite the wildly reprobate ways of this or that person, a person turns out to be a better person than the parent. These cases of God-fearing and decent men born of wicked ancestors is something mysterious. That mystery doesn't seem to be "good upbringing" unless we're going to imagine that King Saul was a totally awesome parent. Actually, maybe he was a great parent but happened to be a corruptable leader everywhere else. It's tough to say with certainty.