I feigned shock.

"Whoa. Why would she do that?"

"I don't know!" 16 said, shaking her head. "She's so nosy."

16 didn't know it, but I could understand exactly why Jodi's mom would call Sarah's mom with that information. Before I started raising teenage girls, I would've sworn I'd do the very same thing.

But when I was talking to a mom on the phone the other night and she said, "I hope if Julie is ever up to anything, you'll tell me," I knew that in all honesty, I probably wouldn't. The truth is that even though I know things that would send half the PTA board home screaming first for their daughters and second for the phone number of the nearest convent, I keep it to myself. Because my first allegiance is to my girls. Period.

I treasure the fact that they feel like they can tell me who's drinking and who's doing drugs, who's getting hickeys on which parts of their bodies, who cheats on all his tests and who toilet papered the neighbor's house the other night. I want to keep that openness going between us for as long as possible.

At the same time, I feel a little bit guilty when I see the moms of these kids, because truthfully, I'd want to know if I were them. And yet, I can't betray my girls. I just can't.

There are exceptions, of course. If a child's life were seriously in danger, I'd tell. Sensitively. Anonymously. I've done it before and I don't regret the decision.

But even that leads to gray areas. What about the girl who brags about using cocaine? Or the guy known for driving 90 mph everywhere he goes? What about the binge drinkers? The bulimics? If I started tallying up the potentially dangerous situations brewing among my stepdaughters' classmates, I'd be on the phone all day.

I understand if you disagree with my decision to keep my information to myself. Plenty of my friends do, particularly the ones with young children. They think I'm breaking some sort of mothers' code by not telling other moms what's going on with their teens. But if I lost the trust I've spent years cultivating in my girls, I would never forgive myself.

And I don't expect anyone to tell me about my kids, either. Instead, I've developed a hyper awareness stealthily covered by studied nonchalance. I wouldn't call myself a snoop exactly, but I do make it my business to know what's going on, listening to backseat conversations between the girls and their friends, reading their MySpace pages, and asking lots of casual, carefully-spaced questions. In the end, if I don't know what's going on in their lives, I have no one to blame but myself.