A new report from Johns Hopkins University quantifies what teachers have always known--a lot of students are chronically absent. The handful of states tracking not just absences in the aggregate but also the patterns of absenteeism by individual students report that somewhere between 6 and 23 percent of the student population is routinely absent. In high poverty urban areas the rates are even higher, as much as 33 percent. Some high schools have 75 percent or more of their students regularly missing class.

The notion that schools (and by connection, states) ought to be tracking student patterns is brought home by a simple calculation. A school could be reporting a 90 percent overall attendance rate, the researchers estimate, while as many as 40 percent of its students miss more than 10 percent of the year. Interestingly, researchers found that the primary factor associated with absenteeism was income. In fact, gender and race did not appear to factor in at all.

Students' buckshot attendance is not just debilitating to their academic success, it is also endlessly challenging for their teachers. Fortunately, some states are beginning to invest in the creation of early warning systems to identify students at risk of dropping out, with chronic absenteeism serving as a primary indicator. For educators and policymakers to properly assist chronically absent students, designers of the early warning systems would be wise to allow for tracking the causes of students' absences as well.

On a related issue, there's some debate over whether teachers ought to bear some responsibility for absenteeism. Districts like Buffalo, New York, are struggling to determine how the performance of students with chronic absenteeism should factor into teachers' evaluations. Those decisions raise an important question: who is responsible for students with shaky attendance? Another issue is school funding, often dependent upon physical student counts and frequently decried as being much depressed in schools that struggle with absenteeism. Having more data on student absences will be invaluable to advancing those and other discussions thoughtfully.