A few years ago, I got a call from the children’s school. “I’m so sorry,” said the voice on the other end of the phone, “but we’ve found a live louse on [child].”

“Oh, no,” I responded. The school knew we’d been treating for lice — I’d alerted it earlier in the month. “Just one?” Yes, just one. The caller had looked for more but seen nothing. “We’ll have to treat her again tonight! Thanks.”

I hung up and went back to work. About 45 minutes later, the phone rang again. “Excuse me,” said the same voice, politely. “Are you going to come get [child]?”

Well, no, I wasn’t. It hadn’t occurred to me that one louse removed by the school was grounds for removing the child from the school. I was wrong, of course, very wrong (and any of my fellow parents will recognize immediately that I must have been a fairly young parent myself at the time). But the school in question had a firm, and common, policy: at any sign of head lice, the child is out.

Because policies vary, even in different schools within the same district, I can’t find hard numbers on how many schools will send home a student for the presence of lice or nits (lice eggs). Anecdotally, and based on a purely unscientific survey of friends, acquaintances and a few pediatricians, many (if not most) schools, like mine, ignore the recommendations of both the C.D.C. and the American Academy of Pediatrics. According to the C.D.C:

“Students diagnosed with live head lice do not need to be sent home early from school; they can go home at the end of the day, be treated, and return to class after appropriate treatment has begun. Nits may persist after treatment, but successful treatment should kill crawling lice. Head lice can be a nuisance but they have not been shown to spread disease. “

“But that’s a hard sell,” says Dr. Kenneth Wible, director of the pediatric care center at Children’s Mercy Hospitals in Kansas City, Mo. “I’ve had school nurses tell me that they don’t care what the research says. Their 30 years on the job tells them that if they leave children in the classroom with lice, they’re going to get more children with lice.”

Our lice odyssey lasted that entire school year; for a variety of reasons (inconsistency of treatment, the use of treatments to which many lice are now resistant, attempts to spread expensive treatments among several family members, and the sheer number of people infested in our household), we just couldn’t get rid of them.

It’s possible we were simply reinfected. It’s more likely that I missed a nit on my own head or that of my long-haired son, failed to do a timely retreatment, and the whole cycle slowly, inexorably, started again.

Over the course of that year, I learned firsthand what schools don’t tell you about those no-lice-no-nit policies: they incentivize parents to lie, or at least to sin by omission. What working parent would own up to lice when the result will be vigilant school officials ready to send a child home at the first sign of dandruff? In our case, those vigilant officials left one of my children in tears at the thought of school; every morning, before allowing her into the classroom, someone would part and search through her hair, and every teacher she came in contact with repeated the search throughout the day, leaving her miserable and self-conscious.

As the recalcitrant, failed parent, I have some feeling that I (although not my daughter) deserved all of that: how could I let the lice get such a hold, and how could we fail so consistently to get rid of them? I never knowingly sent a child to school or to a friend’s house with lice. But I stopped telling the school when we had found and treated them yet again, and I told the children to volunteer nothing. It’s fair to say that I should not have done either. A better person would have both been able to more quickly defeat the problem, and would have owned up every time in order to allow other parents (somewhere out there lay the source of our lice; I cannot be blamed for everything) to check their children’s heads.

After reaping the harvest of that first honest report, I kept quiet. We learned to comb better, we learned to treat the children at least twice, and we learned to braid the girls’ hair very tightly before sending them off to school. Dr. Wible agreed with me that the best response is a treatment immediately and one in just over a week to kill any newly hatched lice. (No treatment has been proved to completely kill or remove the nits that hatch in about that amount of time.) As for products designed to prevent lice from settling on your child? I admit it, I bought some. An expert I spoke with in reporting last year laughed, and offered to sell me a magic spell that he guaranteed would be just as effective.