Two new studies and results from a pilot program surfaced this month that try and get to the causes and effects of teacher absenteeism. The ill effects on student performance are clear, say Harvard researchers, who not surprisingly quantified a measurable decline in student achievement when teachers are frequently absent. The impact of a teacher absent ten days is roughly comparable to what a number of studies show is the significant difference between a child getting assigned a first-year teacher instead of a second-year teacher.

As for the causes of teacher absenteeism, a study from Australia suggests that school culture plays a big part in how often or why teachers in any given school choose to take sick leave. Researchers found that within several months of teachers starting a new school assignment, they adopted the average rate of sick leave at the new school. In some schools, it's no big deal if you take a day off for the sniffles, birthday or "mental health" day. In other schools, it's just not done, so teachers essentially suck it up.

These findings are echoed by the results from a recent pilot program in Palm Beach County, in which teachers in 20 schools were paid to show up more often. Under the pilot, teachers could either cash in their unused sick leave at the end of the year or earn a bonus if rates of school absenteeism fell. However, the pilot was a dud. Only five of 20 schools actually decreased their absenteeism rates.

Among the five successful Palm Beach County schools, principals attributed their success to their practice of having other teachers cover for those who stayed home--instead of using substitutes. Teachers think twice before saddling their colleagues with their students all day. "Sometimes when your peers have to pick up the slack you feel guilty. It was kind of like peer pressure," noted a principal in one of the successful schools, who added that the "district tangled a carrot, and we took it."

In contrast, the principals leading the schools with high absenteeism dismissed the very notion of of the need to reduce teacher absenteeism, explaining that teachers can't control when they are or a family member is going to get sick. As one principal explained, "The teachers try very hard [to be] here because it puts more work on them when they're out of school,...things happen. You have to be there. Family is number one."

No matter the causes of absenteeism, when substitutes report for duty, it's not just teachers who get a day off.