Charters that don’t fill student vacancies may find it easier to boost test scores

Most DC charter schools have a policy of accepting new students at any grade level. But others refuse to take applications past a certain grade. Because students who arrive in later grades can bring down a school’s overall test scores, we need to be careful when comparing schools that have different admissions practices.

All schools have some attrition from one school year to the next. Some charter schools backfill, which means they accept new students to fill slots that become vacant. Schools that don’t backfill don’t replace those students, allowing the size of a grade cohort to shrink from year to year.

In some places, like New York and Philadelphia, the backfill issue has divided the charter community. Some have argued it’s unfair not to replace students who leave, given the length of charter waitlists. They also say schools that don’t backfill are artificially inflating the percentage of students who score proficient on standardized tests.

That’s because the most mobile students tend to score the lowest. And students who have been at a good school since early childhood are more likely to be on grade level and better accustomed to a school’s behavior code than those arriving later on from weaker schools. So if a school doesn’t replace those who leave, it can end up with a smaller cohort of higher-scoring students.

At one New York City charter school, for example, the percentage of students in one cohort who scored proficient in math was 94% in 3rd grade and 97% five years later, in 8th grade. But the number of students taking the test over that period declined from 88 to 31. That school is part of the Success Academy network, which doesn’t backfill after 4th grade.

But schools that choose not to backfill aren’t necessarily just trying to inflate test scores. The leader of the Success Academy network says she’s protecting the interests of students who stay the course. When new students come in who are far behind, they absorb teachers’ attention and hold back those ready to move at a faster pace.

And choosing not to backfill has a cost. In places like DC, where schools are funded on the basis of the number students they enroll, lower enrollment means less money.

Some DC charters don’t backfill

DC charters aren’t publicly sniping at each other over the backfill issue, but some schools here appear to be reaping the kinds of advantages critics have pointed to elsewhere.

Two DC charter middle schools, both of which include grades 4 through 8, don’t accept new students after 6th grade. Both are high-performing and serve primarily low-income populations, and both had significant declines in enrollment for the cohort that graduated from 8th grade in 2014.

At one of the schools, Achievement Prep, that cohort dropped from 93 students in 6th grade in 2012 to 43 in 8th in 2014. The proficiency rates for 8th graders in 2014 were 90% in reading and 97% in math.

At the other, DC Prep Edgewood, the cohort dropped from 55 to 32. The proficiency rates for its 8th graders were 81% in reading and 100% in math.

Would those schools’ 8th-grade scores have been lower if they’d filled vacancies with new students? It’s hard to say. But another charter middle school that accepts new students at all grades, E.L. Haynes, maintained a class size of 101 between 6th and 8th grade for the same period. Its 8th-grade proficiency rates in 2014 were significantly lower than the two schools that don’t backfill: 57% in reading and 70% in math.

Even high schools that backfill don’t necessarily admit many new students

It’s more common for charters not to backfill at the high school level. Eight DC charter high schools restrict applications to certain grades, with two high-performing ones—BASIS and Washington Latin—not accepting new students after 9th grade.

But even high schools that theoretically accept students at all grade levels can see their cohorts shrink dramatically. At highly ranked KIPP College Prep, the 2015 graduating class numbered 71 students, down from a 9th grade cohort of 134. Last year, the school enrolled only two new 10th graders and one new 11th grader, according to a KIPP DC spokesperson, Lindsay Kelly.

Why not more? “Unfortunately,” Kelly said in an email, “many students who come to us in high school lack the credits needed to be on track with their grade level. Some families would rather have their child be promoted at a different high school than have them repeat a year as a student at KCP.”

Should all charters be required to backfill?

Some argue that all charter schools should backfill, to level the playing field. New Orleans, where almost all students attend charter schools, has imposed that requirement.

But as KCP’s situation illustrates, enforcing such a rule might not be that simple—or even desirable. It doesn’t seem fair to hold back students who are capable of doing grade-level work or better by requiring their schools to admit students who are far behind.

Perhaps the better option is to be clear about what we’re comparing. New York is considering investigating the amount of attrition and backfilling at its charter schools, which seems like a step in the right direction.

It would also help to look not just at a school’s proficiency rates, but at how much its students test scores grow from year to year. DC’s Public Charter School Board does take growth into account in evaluating schools, but it’s hard for the public to tell how much weight they place on it.

And we should be able to compare test scores for students who have been at a school for several years against scores for newcomers. Right now, those two categories are lumped together, at least for public consumption. If schools that backfill are nevertheless able to boost achievement for kids they’ve had for a while, they should get credit for that.

The controversy over backfill is a variation on the controversy over charter schools in general. Yes, charter schools have an advantage over traditional public schools because, among other things, they don’t have to take students midyear—and because families who choose to apply to charters are more likely to be motivated and engaged.

And yes, charters that choose not to backfill have advantages over charters that do backfill, as well as over traditional public schools that backfill. But rather than imposing the same burdens on all schools, we would do better to acknowledge that some schools have more obstacles to overcome than others.

Cross-posted at DC Eduphile.