Teacher turnover – the rates at which teachers leave the profession and switch schools – is obviously a very important outcome in education. Although not all turnover is necessarily a “bad thing” – some teachers simply aren’t cut out for the job and leave voluntarily (or are fired) – unusually high turnover means that schools must replace large proportions of their workforces on an annual basis. This can have serious implications not only for the characteristics (e.g., experience) of schools’ teachers, but also for schools’ costs, cohesion and professional cultures.

According to the most recent national data (which are a few years old), annual public school teacher turnover is around 16 percent, of which roughly half leave the profession (“leavers”), and half switch schools (“movers”). Both categories are equally important from the perspective of individual schools, since they must replace teachers regardless of where they go. In some subsets of schools and among certain groups of teachers, however, turnover is considerably higher. For instance, among teachers with between 1-3 years of experience, turnover is almost 23 percent. Contrary to popular opinion, though, the relationship between school poverty (i.e., free/reduced-price lunch rates) and turnover isn’t straightforward, at least at the national level. Although schools serving larger proportions of lower-income students have a larger percentage of “movers” every year, they have a considerably lower proportion of “leavers” (in part due to retirement).

This national trend, of course, masks considerable inter-district variation. One example is the District of Columbia Public Schools (DCPS).

According to data released last year (via Steve Glazerman), which applies to the 2011-12 school year and is summarized in the table below, DCPS loses about 25 percent of its teachers every year. The vast majority (about 19 percent) of those are “leavers.”

(Bear in mind that these 2010-11 DCPS figures are not directly comparable to the national data cited above. For instance, the national data apply to 2008-09, and include part-time teachers. Also, the administrative datasets upon which the DCPS estimates are based cannot differentiate between “leavers” who leave the profession entirely and those who simply leave DCPS because they got a job in a different district [including, perhaps, a DC public charter school]. Still, once again, the mover/leaver distinction is somewhat trivial from the standpoint of a school, which must replace a teacher regardless of where they go.)

One of the most salient features of the table is the rather startling discrepancy in DCPS turnover rates between schools with low-to-medium poverty rates and those with high poverty rates (in the table above, high poverty schools are those with greater than 80 percent FRL). Whereas turnover rates are roughly 17 percent in low- and medium-poverty schools, they are a somewhat stunning 38.4 percent in high-poverty schools. To the degree these figures do not fluctuate between years, this means that this subset of schools must replace, on average, almost two out of five teachers every single year.

Now, it’s important to note, first of all, that this level of churn, overall and/or in how it varies by school poverty, may not be unusual for districts similar to DCPS (for example, the overall rate of 25 percent is probably roughly comparable to other big city districts). In other words, this may be less a DCPS problem than a large urban district problem (and the raw figures certainly cannot be chalked up to specific policies, in DC or elsewhere).

Moreover, it’s unclear how much of the discrepancy in attrition/mobility by poverty rates is due to working conditions per se. For one thing, as seen in the DCPS document linked above (see page 36), teachers in higher-poverty schools receive lower ratings, on average, from DCPS’ teacher evaluation system than their counterparts in medium- and low-poverty schools, which means that some of the turnover may be involuntary (i.e., dismissals). Also, leavers and movers have lower evaluation scores, on average, than stayers (see the table above, and also that on page 32). Similarly, there are other variables, such as experience, that may mediate the association between school poverty and teacher turnover.

In any case, while some turnover is inevitable and some of it (e.g., low-performing teachers) can be seen as beneficial, the situation in the highest-poverty DCPS schools, where around 40 percent leave every year, is at least a cause for concern. It’s difficult to comprehend how schools can function effectively under such conditions.