A head louse is about the size of a pinhead.

Montgomery, Ala. ? For generations, children with signs of head lice were summarily sent home by the school nurse to their everlasting shame. Now schools have become less nitpicky.

With the backing of some major health organizations, a majority of schools nationwide are allowing youngsters to stay in class if they have nits — that is, lice eggs — but no crawling lice in their hair.

It’s a change recommended by the American Academy of Pediatrics and the National Association of School Nurses, and it has been welcomed by many educators and parents.

“Our children miss enough school without having to add this to it. The no-nit policies are as much a nuisance as the pests that we’re dealing with,” said Astrid Cruz, a mother of three from Palm Coast, Fla.

When Cruz’s daughter got lice in second grade and was removed from class, Cruz had to beg administrators to let the girl ride the school bus home. When more nits were spotted, the girl had to miss school and go to work with Mom.

Other parents, like Debbie Cornell, want to see schools go back to a hard line against head lice. Cornell grew frustrated when her daughters got head lice twice last school year. Their San Francisco private school lets kids with nits stay in class.

The U.S. has anywhere from 6 million to 12 million cases of head lice each year, said Dr. Barbara Frankowski, a Vermont pediatrician. It is not clear whether there have been more infestations as a result of the new, more relaxed policies.

The switch came after a 2002 pediatrics academy study said students with nits shouldn’t be kept out of class. The real problem, according to the medical experts, is the lice, not their eggs.