(Names have been changed to protect the innocent, and the moderately-guilty).

As much as we like to think we are our children’s best teachers, it’s the time they spend with friends that provide them with the most “education.” Case in point: the few days our 8-year-old, let’s call him Huck, spent at baseball camp last month. At camp, the counselors teach batting, fielding, throwing and chewing bubble gum. The campers teach scratching, spitting and singing rude songs. Huck comes home singing about Batman peeing on the wall, Scooby Doo eating poo and a word-play game that he generously teaches his five-year-old brother: “Hey, Butch,” he whispers to him with a sly smile, “say ‘X’ really fast, over and over.”

Butch, pleased to be enlisted in his brother’s game, says: “X X X X X X X.”

Huck giggles uncontrollably. “You said, ‘Sex sex sex sex sex sex sex!’”

Butch is unperturbed. To the contrary, he thinks it is the pinnacle of humor. They keep at it. They sling “X X X X” all over the neighborhood. It’s getting a little out of control. My husband, Stud, decides he has been handed a “teachable moment.” It is time to Talk About Sex.

It’s not like we haven’t talked with our children before about where babies come from. They have long known that a man’s sperm fertilizes a woman’s egg, leading to the development of a baby. They have had long chats about the games they played together as lonely eggs in my ovary, waiting to become zygotes and begin their cells dividing. A sleepy, sluggish three-year-old Butch once commented, “I’m not feeling very fertilized right now.” (Truly, I could not make this stuff up.)

They also know that babies, including them, come out through a woman’s vagina, or sometimes her stomach.  But they have never asked The Big One: how do the sperm and ovum end up at the same party?

I always expected to be the one to have The Talk. After all, two years ago Huck asked my husband, “Daddy, how do babies get inside Mommy’s tummy?” and his wise father replied, chin in hand, “Good question. You should ask Mommy about that some time.”

But this time, amidst the chorus of “sex” reverberating through the house, Stud decides to step up to the plate. “Do you know what sex is, guys?”

“Yes.” Butch replies. “It means kissing.”

“No,” Huck counters, “it’s naked cuddling.”

I listen from the other room as Stud takes a swing. “Sex,” he explains, “is when a man puts his penis in a woman’s vagina, because they want to make a baby.”

Silence. No laughter. Shock has set in. For all of us.

I listen for a sound, anything. Finally, Butch speaks: “I’m hungry.”

And so we move on . . . .

The next day the four of us go to see Alvin and the Chipmunks. We are sitting in the dark movie theater waiting for the previews to end. Two on-screen characters kiss. “That’s sex, right mom?” Butch asks.

Thank goodness I overhead their dad’s explanation yesterday. I repeat it, adding for good measure: “ . . . because they love each other and are married.” I consider adding that the man and woman have Ph.D’s, but let it go for now.

“Oh yeah,” Butch says, and the movie begins. Sexy girl chipmunks fawn over Alvin, Simon and Theodore and shake their rumps singing Beyonce’s Single Ladies. Horny teenage boys threaten Alvin because species-blind teenage girls have swooned and sighed over these rodent rock stars. Sex is everywhere.

Walking home later, Butch explores every leaf on every plant. I watch him, marvel at his concentration, wonder at his inner conversation. Out of the silence he asks in the slow, articulated voice he has, “Can I play with Kevin tomorrow?” He considers the leaf in his hand. “I want to tell him what sex is.”

Uh-oh.

I envision him becoming the scourge of the pre-school, the playmate to avoid. “Well, honey,” I try to appeal to his sense of propriety, “that’s something his mommy and daddy want to tell him about. It’s not for friends to tell.” I almost add, “Kind of like Santa Claus,” but that would just complicate matters. Butch seems to understand, but his eyes betray significant disappointment. “I wish I could tell him,” he adds.

“I know, honey. But please don’t.”

We get home and I e-mail Kevin’s mother an advance apology for the things my son will no doubt teach hers, not just in pre-school but over the next thirteen years. I get a frantic reply from her, wanting to know exactly what words she should be prepared for. When I tell her over the phone the words we used, verbatim, I hear the now-expected silence, and wonder if the phone has gone dead. Then I hear her breathe. “Wow,” she sputters. “You guys left nothing to the imagination.” Yeah. We figured it was best that way.

And I wonder as we say goodbye, if maybe we’re all going to be on the “playmates to avoid” list for a while.