Last year was a hellacious year for lice outbreaks. My four older children and me got those little buggers numerous times. The school nurse said it was the worst she'd seen since 1997 when she started working at the school. Now, my kids weren't sent home, I discovered them after they complained that their heads were itching. I treated, made sure all the live bugs were out and the following day they went back to school, but were checked by the nurse before they could go to class.
I get that they pose no health risks and aren't physically dangerous. Do I think kids should miss school if they have nits (lice eggs)? No, I don't. The eggs are so firmly embedded on the hair shaft that they don't pose a risk. Do I think a kid should be allowed at school when they are known to have live bugs crawling through their hair? Hell no I don't.
According to these articles, kids are more likely to catch lice outside of school than at school. They list playdates, overnight camps and sleepovers as possible primary sources. I call bullshit. My kids don't go to overnight camps, rarely have or attend sleepovers and are pretty much past the age of playdates where they roll around and climb on top of each other touching heads etc. I don't know about at your kid's school, but at my kids' school, they share headphones when working on the computer and they have a "comfy couch" in the classroom that the kids are allowed to sit on at various times during the day. Both of those are great opportunities to pick up little bugs. Is it unlikely? Maybe, but I can promise it is even more unlikely that they are getting them from home.
The fact that they pose no health threat is debatable. Maybe no physical health threat, such as disease, is present, but you'd better believe there is a mental health threat - my mental health - which inadvertently threatens the well being and safety of my children, husband and anyone else I may come in contact with at any given time. Have you ever come across a mother who has had to sit and comb through five children's hair, three of whom range in ages from eight to ten-years-old and have long hair, and then had to sit through their husband combing through their hair? All the while boiling hairbrushes and washing sheets and pillows and putting stuffed animals in to black garbage bags in hopes of suffocating the little bastards? (The lice, not the kids.) If you haven't, be glad. It is not pretty.
I was up until almost midnight one night going through my daughter's hair and guess what? She didn't go to school the next day. Not because there were still live bugs in her hair, but because she was up past midnight and was utterly exhausted. To do a thorough job of getting the nits out you have to basically check every strand of hair and that takes a shit ton of time. Let me tell you, buy the time I had to do that for the fourth time over the course of about three months, I was done, exhausted, spent, beyond frustrated. I seriously contemplated shaving everyone's heads just so I wouldn't have to do it again.
There was a girl in my son's class who continued to have lice throughout the year. One of my other daughters said she actually saw the bugs crawling through the hair of a girl she sat next to because they were so big and she had so many. We had to postpone my other daughter's birthday party, miss another child's party and cancel plans to go to the annual parade because I was yet again combing through the hair of five children and myself. I would be irate if I found out any of my kids went to a sleepover at someone's house, or to a birthday party of a child whose parents knew they had lice and I wasn't at least given a courtesy heads-up.