I’m in the cleaning-supplies aisle at the supermarket, pulling with all my might on a plunger stuck to the floor. Shoppers stare as they squeeze around me. I want to apologize, but I don’t dare. If I did, I’d have to look up from the floor and let all those mature, responsible adults see that I’m quietly laughing my head off.

If anyone else were struggling to remove a plunger her 9-year-old had stuck on the floor, I’d have every right to laugh. But of course you don’t do that when you’re the mom. The mom is supposed to take these matters seriously. She’s supposed to give her child the look. She’s supposed to speak in the tone. The last thing in the world she’s supposed to do is laugh. That just might make her child think a shopping trip wouldn’t be complete without a plunger stuck to the floor.

But do I really have to stifle myself until Kevin goes off to college? Aren’t there any other mothers out there who have this problem?

Goodness knows my mother doesn’t. I swear she was born with the demeanor of Mother Superior. She takes pride in telling people about the time, when I was 3 years old, that I looked up at her after doing something naughty and said, “Mommy, make a pretty face.”

I suspect most women, though, lose their sense of humor along the way to motherhood, probably around the 23rd hour of labor. Take my friend Lori, for instance. Lori managed to raise two responsible teenagers who wouldn’t dream of sticking a plunger on a supermarket floor. But in college, she had no more control over the giggles than I did. I realized that one day in microbiology class, when the professor walked in from outside with two windblown tufts of hair sticking up like a devil’s horns. Lori and I were in stitches. Just as one of us started to calm down, we’d look at the other and start tittering all over again. For some reason I still don’t understand, nobody else in the class laughed. I suppose they were honing their parenting skills.

Of all the times Kevin makes me laugh, the most embarrassing are when he has no intention of being funny. Like when he sings. Ever since a nun made me move my mouth to avoid throwing everyone else off at the Christmas concert in fifth grade, I’ve been too self-conscious to sing anywhere but in the car with the windows shut. I didn’t want my son to grow up like that. So from the time he was born, I started singing to him in the car with the windows shut.

Then one day, we were driving along when a song he knew came on the radio. He started singing. I’ve never heard anyone so flat, so incapable of carrying a tune, so much like me. I tried to control myself. But it was more than I could bear. I burst out laughing. Furiously, I racked my brain for an excuse. I told Kevin I was laughing about something our neighbor Bill had said the day before. I went on to explain that Bill pointed out, truthfully, I might add, that every third word out of our neighbor Roger’s mouth is “subsequently.” Kevin never questioned my laughing at something I’d heard 24 hours earlier. He knew me too well.

Another time Kevin gave me a fit of giggles without trying was when he called his friend Christian and Christian’s mother picked up the phone. “Hi Sheila,” he said. “This is Kevin.” Sheila? To a fourth-grader? That’s like me calling the queen of England “Liz.” I started giggling, which made Kevin laugh. Now Sheila not only thinks my son is all too casual addressing adults, but downright rude, too.

Church, of course, is one place where every parent must show by example that it’s never appropriate to laugh. I wish to God I knew how. Husband Bob, Kevin and I were in church one Sunday listening to a priest with a heavy foreign accent. The priest wanted to teach us the importance of keeping our word. Instead, he told us to “keep our wood.” Nothing funny about that, I told myself. I’m in church. I am not going to laugh. Then the priest told us again to keep our wood. I squeezed my lips together and stared at my lap. The third wood was the killer. My shoulders started shaking. Tears rolled down my cheeks. I fought to keep from laughing out loud. Everyone around me was stoic as you’d expect people listening to a sermon on harboring lumber to be. Everyone, of course, except Kevin.

Life has changed a lot since those days. Now that Kevin’s 16, I see him in spurts, usually when I’m driving him from school to Kyle’s house, or Kyle’s house to Taylor’s house, or Taylor’s house to Max’s house. The few waking hours he spends at home are in his room, texting Kyle, Taylor, Max, and every other teenager within a 25-mile radius. I’m grateful, though, that one precious thing hasn’t changed.

I was reminded of that recently, when I took Kevin to an empty parking lot to teach him how to drive a stick shift. He jerked forward then stopped, then jerked, then stopped, right in front of a group of teenagers he barely knew. At his age, I would have dove under the seat. Not Kevin. He laughed. Then he waved, beeped the horn, and kept right on jerking around the parking lot, waving and beeping every time he passed the kids. When we finished 20 minutes later, he still didn’t know how to drive a standard. But who cares? We had a ball.

Other parents may count on their kids to finish their homework on time, do the dishes or take out the trash. I count on something better; I count on my son to make me laugh.