Miranda: Teenage girls are mean, and if you survived junior high you know this. Once a girl hits that 14- to 15-year-old mindset, she can become so devious it leads to destructive behavior.

We tend to be competitive, overthinking creatures as it is, but something about the high school environment turns this toxic.

Anyone seen “Mean Girls”? It’s based on a book by Rosalind Wiseman called “Queen Bees and Wannabes.” Cady likes Aaron, but Regina steals him away by telling him that Cady is stalking him, then Regina proceeds to throw herself at the clueless boy. While the movie is humorous, it points out the flawed way that teenage girls relate to each other.

Stealing a boyfriend is inexcusable. Let others sort out their own relationships because if you choose to ruin someone else’s, then you are giving permission for another girl to ruin yours. Sometimes we get too wrapped up in drama and too consumed by the situation. Take a step back before you choose to do something like this. Ask yourself, “What will I think of myself in a year?”

Now that social media like Facebook and Twitter have given us the ability to put anything out on the Internet at anytime, we’ve developed a phenomenon described as “keyboard courage,” where we say things online that are meaner or more brazen than what we’d say in person.

Here’s a hint: Before you hit “send” on that tweet or text, think about the worst possible consequences. Just turn off your cellphone and your computer, go outside and think. If you can rise above this teenage girl mindset, you will thank yourself down the line.

Dr. Wes: Miranda’s certainly on a roll with this one, and for good reason. She’s hit upon the less-than-civil way teens (and a whole lot of adults) show callous disregard for others in our social interplay.

And yet there’s more. Over the last 10 years girls have really taken charge of their sexuality and dating (there’s a quaint old term). This sounds kind of empowering when I put it that way, doesn’t it? But with this new power comes a great many problems and not as much responsibility.

We’ve discussed many times the lowering of the threshold on sex so that an actual relationship is, for many girls now, optional. No wonder some authors have called girls “the new guys.” As one of the old guys, I don’t take that as a compliment.

Unfortunately, this new empowerment has also influenced what I refer to as a “market economy” of dating in which teen girls compete intensely (and as Miranda notes, sometimes viciously) for optimal partners.

I don’t know how to put this delicately, but girls who are willing to hook up easily and without benefit of relationship are essentially undercutting the market, making it more difficult for the rest to compete and maintain their standards. It sounds crass, but most teenage girls I’ve pitched that concept to agree that it describes Dating 2012 pretty well.

I realize the word “ethics” appears twice a month in our column, but nowhere is it more relevant than in this one. Parents really need to establish from early on a clear guideline for how people interrelate, then practice it themselves and hold their teens accountable to it. If you find that your daughter (or son) is violating those guidelines, study the situation carefully and comment. It’s okay to remind kids of the impact they have on the world. If parents don’t do that, who will?

If being a kind and ethical person isn’t a good enough incentive for your freshman or sophomore, just remind her that she’s going to be stuck in the same high school for the next couple of years with all those other girls, and after that, maybe one of the local colleges. There she’ll have to look some of them in the eye and imagine what’s on their minds when thinking of her. Worse, some of her peers are going to grow up and be in charge of stuff — schools, companies, social groups, courts, etc. She may need that social network someday. And won’t that be an awkward moment when her prospective boss looks over her glasses and says in that special voice of knowing power and disdain, “Oh … I remember you. We went to high school together.”