Education officials like to say that kids can't learn if they aren't in school.

But what if teachers aren't in school?

While absenteeism is usually considered a student matter, in San Francisco - and many other districts - the average teacher misses more school than the average child.

If last year's numbers hold steady, the 4,100 teachers in San Francisco, on average, will each be absent about 11 times this school year, about once every three weeks. That's four to five days more than a typical student, out of 180 days total.

About seven of those days were for sick or personal leave, and the rest were training days offered or required by the district.

While the teacher absentee rate is about average, or even a smidge below average, for large urban districts across the country, it's a lot higher than other industries, where the typical worker takes about four sick or personal days over an entire year.

In San Francisco, where classes start Monday, teacher absences gained attention last year when the district struggled to find enough substitutes to fill classrooms the day before Thanksgiving break, when more than 1 in 10 teachers called in sick, took the day off or were in training. Similar spikes in absenteeism happened several other times on a Friday or before three-day weekends.

Teacher aides

Teacher aides, who are especially critical to special education classrooms, were also absent in greater numbers on certain days, with 16 percent of the 1,480 aides out sick or on personal leave the Friday before Labor Day.

San Francisco again isn't alone in this Friday phenomenon.

Yet few districts have sought to understand or address teacher attendance issues, said Nancy Waymack, managing director of district policy at the National Council on Teacher Quality, which recently released a national study on teacher absenteeism.

"There hasn't been a lot of attention paid to it," she said. "I see it as an area where districts can improve and make a real difference."

Twenty percent of San Francisco teachers were absent three days or fewer in 2012-2013, according to the national report, which analyzed data from 40 urban districts.

"One in 5 is doing a great job of being there every day," said Waymack, a former San Francisco school district administrator.

Parent Ellen Schatz has two children in San Francisco schools and is the PTA president at Miraloma Elementary School this year.

Over the years, she said teacher absenteeism hasn't been a problem for her children's classrooms.

"What I see is teachers really making an effort to not miss days even if a normal person might call in sick," Schatz said. "I've seen teachers come in with knee braces and back braces and stuff like that."

But 13 percent of the district's teachers were chronically absent, missing more than 18 days out of 180 - one, two or three days at a time. Those on disability or maternity leave were not included in that count.

"I think that is a lot," Waymack said.

Yet it's actually lower than the norm across the 40 districts studied, where 16 percent were chronically absent.

In San Francisco, teachers contractually get 10 days of sick leave each school year, seven of which can be used for personal days. Unused days roll over.

They don't have to ask permission when they are taking a personal day or tell a supervisor they are out sick. They call an automated system to request a substitute.

Last year, teachers took more than seven days of sick or personal time, on average. On top of that, the district increased professional development or training days to help teachers.

Substitute supply

District officials quickly discovered they needed to mitigate problems associated with teachers being increasingly out of the classroom. For starters, the district realized last year that Monday and Friday trainings were exacerbating the higher teacher and aide absentee rate on those days, potentially maxing out the supply of available substitutes.

"We're not going to do professional development on Fridays or Mondays," said Monica Vasquez, the district's chief human resources officer. "If folks are going to take a long weekend, they're going to take a Friday or Monday."

Dennis Kelly, president of the United Educators of San Francisco, also suggested that the system ensure an adequate supply of substitutes and to look at training teachers during the summer months rather than pulling teachers out of class. It's an expensive proposition, he acknowledged, but one that should be considered.

It's also important to understand the demands of teaching, the support or lack thereof teachers get at schools, and how all that has an impact on attendance.

Teaching is hard, said Richard Swerdlow, a veteran teacher in San Francisco.

"Teachers work in very crowded rooms," he said. "There are not many jobs where you're in an enclosed space with 30 people."

Sick children often come to school, where flu can spread like wildfire.

"Parents sometimes have to go to work, and they have no place to stash the (sick) kids, and they send them to school," he said.

Over the years, he hasn't gotten the sense that there's any more sick-leave abuse than in other professions.

"It's so hard to get a substitute and write a substitute plan," he said. "You often err on the side of going in."

A handful of districts across the country have attempted to mitigate teacher absenteeism using various strategies, including measuring attendance in teacher evaluations or rewarding good attendance with tickets to sporting events.

In an unusual move, Cincinnati rewarded excellent attendance with more personal leave.

Bringing issue to surface

None was universally effective, although in Boston, officials required teachers to call a supervisor when they were going to be out, which did reduce the absentee rate, Waymack said.

In San Francisco, district officials say teacher attendance needs more attention.

Human resources staff will be signing up more substitutes to be available for the demand while also studying data to see if there are particular schools, positions or circumstances resulting in higher absenteeism, Vasquez said.

And the district says it will be putting effort into recruiting great teachers and teacher aides who want to be in San Francisco classrooms while communicating the high expectations the district has of its educators, including their attendance.

"Before, we always had enough substitutes. (Absenteeism) wasn't on the radar," Vasquez said. "It's now brought it to the surface as an area that we want to look at."