human capital

Wide margins of error, instability on city's value-added reports

Some English Language Arts teachers received high "value-added" scores in 2007 but much lower scores in 2008.

The value-added reports meant to measure city teachers’ effectiveness have wide margins of error and give judgments that fluctuate — sometimes wildly — from one year to the next, a new analysis finds.

Schools Chancellor Joel Klein has instructed principals to use the Teacher Data Reports as one way to decide which teachers should receive tenure. Teachers who teach English or math to students in grades three through eight receive the reports.

The NYU economist Sean Corcoran found that 31 percent of English teachers who ranked in the bottom quintile of teachers in 2007 had jumped to one of the top two quintile by 2008. About 23 percent of math teachers made the same jump.

There was an overall correlation between how a teacher scored from one year to the next, and for some teachers, the measurement was more stable. Of the math teachers who ranked in the top quintile in 2007, 40 percent retained that crown in 2008.

The Annenberg Institute for School Reform at Brown University, which has a history of criticizing the Bloomberg administration, published Corcoran’s findings, which were part of a wider look at the practice of assigning “value-added” scores to teachers based on their students’ test scores.

The analysis explains the difference between what value-added scores of teachers aim to do and what value-added measurements actually do in practice. The dream is to isolate the effect of a teacher on students’ performance from the effect of everything else; the reality is that the measures approximate that isolated effect with statistics, weak tests, and small sample sizes.

Corcoran offers some praise. “The simple fact that teachers and principals are receiving regular and timely feedback on their students’ achievement is an accomplishment in and of itself, and it is hard to argue that stimulating conversation around improving student achievement is not a positive thing,” he writes. “But,” he writes,

teachers, policymakers, and school leaders should not be seduced by the elegant simplicity of “value-added.”

The weaknesses of value-added detailed in the report include:

  • the fact that value-added scores are inherently relative, grading teachers on a curve — and thereby rendering the goal of having only high value-added teachers “a technical impossibility,” as Corcoran writes
  • the interference of imperfect state tests, which, when swapped with other assessments, can make a teacher who had looked stellar suddenly look subpar
  • and the challenge of truly eliminating the influence of everything else that happens in a school and a classroom from that “unique contribution” by the teacher

Another challenge for the teachers and principals charged with using value-added scores for self-improvement is the uncertainty about what each individual teacher’s score actually is. On each teacher’s report, the city pinpoints the percentile ranking that represents how she compares to other teachers of the same subject and grade.

But while this is the ranking that the teacher most likely holds, it’s far from 100 percent certain. Indeed, the economists who make value-added scores can only be very certain that the teacher falls somewhere on a range of percentiles (and even getting that cautious, they’re still only 95 percent certain). This range, as you might remember from statistics, is called the “confidence interval.”

For most teachers, the confidence interval is at least 30 percentage points long. For math and English teachers with only one year’s worth of data, the average length is over 60 percentage points. That’s a range of, for instance, between the 10th and 70th percentile of teachers.

The average confidence intervals that Corcoran reports are in the chart below. You can see that, because the confidence intervals shrink as the sample size grows, they are longest when only a year’s worth of data is available.

Teachers in the Bronx face the least certainty. Corcoran guesses that this is because their students are the most likely not to be measured, thereby lowering the data pool — either because the students are classified as special ed or English language learners, and don’t take the state test, or because the students move from year to year, making data about their growth over time harder to come by.


The full report is here and below.
The Use of Value-Added Measures of Teacher Effectiveness in Policy and Practice

after douglas

Betsy DeVos avoids questions on discrimination as school safety debates reach Congress

Education Secretary Betsy DeVos prepares to testify at a House Appropriations subcommittee hearing on the department's FY2019 budget. (Photo By Tom Williams/CQ Roll Call)

U.S. Education Secretary Betsy DeVos fielded some hostile questions on school safety and racial discrimination as she defended the Trump administration’s budget proposal in a House committee hearing on Tuesday.

The tone for the hearing was set early by ranking Democrat Rep. Rosa DeLauro, who called aspects DeVos’s prepared remarks “misleading and cynical” before the secretary had spoken. Even the Republican subcommittee chair, Rep. Tom Cole, expressed some skepticism, saying he was “concerned about the administration continuing to request cuts that Congress has rejected.”

During nearly two hours of questioning, DeVos stuck to familiar talking points and largely side-stepped the tougher queries from Democrats, even as many interrupted her.

For instance, when Rep. Barbara Lee, a Democrat from Texas, complained about proposed spending cuts and asked, “Isn’t it your job to ensure that schools aren’t executing harsher punishments for the same behavior because [students] are black or brown?” DeVos responded by saying that students of color would benefit from expanded school choice programs.

Lee responded: “You still haven’t talked about the issue in public schools as it relates to black and brown students and the high disparity rates as it relates to suspensions and expulsions. Is race a factor? Do you believe that or not?” (Recent research in Louisiana found that black students receive longer suspensions than white students involved in the same fights, though the difference was very small.)

Again, DeVos did not reply directly.

“There is no place for discrimination and there is no tolerance for discrimination, and we will continue to uphold that,” she said. “I’m very proud of the record of the Office of Civil Rights in continuing to address issues that arise to that level.”

Lee responded that the administration has proposed cuts to that office; DeVos said the reduction was modest — less than 1 percent — and that “they are able to do more with less.”

The specific policy decision that DeVos faces is the future of a directive issued in 2014 by the Obama administration designed to push school districts to reduce racial disparities in suspensions and expulsions. Conservatives and some teachers have pushed DeVos to rescind this guidance, while civil rights groups have said it is crucial for ensuring black and Hispanic students are not discriminated against.

That was a focus of another hearing in the House on Tuesday precipitated by the shooting last month at Marjory Stoneman Douglas High School in Parkland, Florida.

Rep. Jim Sensenbrenner, a Wisconsin Republican, falsely claimed in his opening statement that Broward County Public Schools rewrote its discipline policy based on the federal guidance — an idea that has percolated through conservative media for weeks and been promoted by other lawmakers, including Florida Sen. Marco Rubio and Utah Sen. Mike Lee. In fact, the Broward County rules were put into place in 2013, before the Obama administration guidance was issued.

The Manhattan Institute’s Max Eden, a leading critic of Obama administration’s guidance, acknowledged in his own testimony that the Broward policy predated these rules. But he suggested that policies like Broward’s and the Obama administration’s guidance have made schools less safe.

“Faced with pressure to get the numbers down, the easiest path is to simply not address, or to not record, troubling, even violent, behavior,” he said.

Kristen Harper, a director with research group Child Trends and a former Obama administration official, disagreed. “To put it simply, neither the purpose nor the letter of the federal school discipline guidance restrict the authority of school personnel to remove a child who is threatening student safety,” she said.

There is little, if any, specific evidence linking Broward County’s policies to how Stoneman Douglas shooter Nicholas Cruz was dealt with. There’s also limited evidence about whether reducing suspensions makes schools less safe.

Eden pointed to a study in Philadelphia showing that the city’s ban on suspensions coincided with a drop in test scores and attendance in some schools. But those results are difficult to interpret because the prohibition was not fully implemented in many schools. He also cited surveys of teachers expressing concerns about safety in the classroom including in Oklahoma CityFresno, California; and Buffalo, New York.

On the other hand, a recent study found that after Chicago modestly reduced suspensions for the most severe behaviors, student test scores and attendance jumped without any decline in how safe students felt.

DeVos is now set to consider the repeal of those policies on the Trump administration’s school safety committee, which she will chair.

On Tuesday, DeVos said the committee’s first meeting would take place “within the next few weeks.” Its members will be four Cabinet secretaries: DeVos herself, Attorney General Jeff Sessions, Secretary of Health and Human Services Alex Azar, and Secretary of Homeland Security Kirstjen Nielsen.

on the run

‘Sex and the City’ star and public schools advocate Cynthia Nixon launches bid for N.Y. governor

Cynthia Nixon on Monday announced her long-anticipated run for New York governor.

Actress and public schools advocate Cynthia Nixon announced Monday that she’s running for governor of New York, ending months of speculation and launching a campaign that will likely spotlight education.

Nixon, who starred as Miranda in the TV series “Sex and the City,” will face New York Gov. Andrew Cuomo in September’s Democratic primary.

Nixon has been active in New York education circles for more than a decade. She served as a  longtime spokeswoman for the Alliance for Quality Education, a union-backed advocacy organization. Though Nixon will step down from that role, according to a campaign spokeswoman, education promises to be a centerpiece of her campaign.

In a campaign kickoff video posted to Twitter, Nixon calls herself “a proud public school graduate, and a prouder public school parent.” Nixon has three children.

“I was given chances I just don’t see for most of New York’s kids today,” she says.

Nixon’s advocacy began when her oldest child started school, which was around the same time the recession wreaked havoc on education budgets. She has slammed Gov. Cuomo for his spending on education during his two terms in office, and she has campaigned for New York City Mayor Bill de Blasio.

In 2008, she stepped into an emotional fight on the Upper West Side over a plan to deal with overcrowding and segregation that would have impacted her daughter’s school. In a video of brief remarks during a public meeting where the plan was discussed, Nixon is shouted down as she claims the proposal would lead to a “de facto segregated” school building.

Nixon faces steep competition in her first run for office. She is up against an incumbent governor who has amassed a $30 million war chest, according to the New York Times. If elected, she would be the first woman and the first openly gay governor in the state.