When girls nationwide miss school Thursday to join in the 6th annual Take Our Daughters to Work Day, children in Runnells, Iowa, will be in classes. The district held the day in February - on a school holiday.

"We think the event is worthwhile," explains superintendent Joseph Drips of the Southeast Polk district. "But we only have 180 days in which to educate our young people. Our cause is worthy too."Fed up with lost academic time and logistical headaches, schools around the country - including girls' schools - are quietly opting out of the annual day held to nurture girls' confidence and ambitions. Educators complain that some students miss school just to sit around a parent's office.

Texas is allowing all schools to reschedule the day. Other schools are limiting participation by grade or actively urging parents to skip the day altogether.

"We're encouraging people not to take part in it," said Jane O'Connell, spokeswoman for New York city's Convent of the Sacred Heart girls' school, which for the first time sent a letter to parents asking them to support its decision "not to observe the program in a way that requires absences from classes."

Over the years, the school grew concerned that students who participated missed important lessons, those who stayed in school felt left out, and teachers had to reteach material. As well, the school heard that some students "just sat around" workplaces, said Mrs. O'Connell.

It wasn't an easy decision for a girls' school to take, she said. But administrators concluded that the school already was actively encouraging girls and exposing them to careers. "Perhaps we do more than a co-ed institution," she said.

Such sentiments are shared by other girls' schools - from New York's Brearley School, which encourages visits to parents' work during nonschool time, to the National Cathedral School in Washington, D.C., which does not actively support the day.

"We're already way ahead in terms of working on girls' confidence and self-esteem," said Cathedral's Tracy Savage.

A number of public schools are also dropping out of the event. Educators are quick to praise the day's intentions, but they say school work comes first.

"When we take children out of school, we're saying the school shouldn't be the No. 1 priority," says Faye Davis, principal of Delaware Elementary, which is part of the Southeast Polk district, southeast of Des Moines.

Officials at the Ms. Foundation, creators of the day, aren't pleased. "Is this a disconnect or what?" asked the foundation's president Marie Wilson in a telephone interview.

Take Our Daughters to Work Day is held on a school day intentionally, she said. In some communities, schools work with Ms. Foundation officials to find places at company programs for children whose parents can't take them to work.

In addition, school follow-up is crucial. "When a girl comes back from a work site and says, `I want to be a physicist,' we want her to ask, `What do I have to study?' " said Wilson.

Not all schools, of course, are opting out. Many educators still staunchly support the event - even while ruing the loss of a school day.

Art Scott, head of the co-ed Webb School in Knoxville, Tenn., gives students carte blanche to be absent, and even e-mailed his teachers this year urging them to bring in as many daughters as possible.

But just as the controversy over whether to include boys in the day still burns year after year, undoubtedly so will the debate over whether to use school time.