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Defense Witness Concedes That the Probationary Period Should Be Three to Five Years

State Defendants and Intervenors called two witnesses, Dr. David Berliner and Ms. Lynda Nichols, to the stand today in the education equality trial, Vergara v. California.

Defendants’ and Intervenors’ first witness of the day, Dr. David Berliner, is a Professor of Education at Arizona State University who testified about the factors affecting student learning and the merits of using value-added models (VAM). During cross-examination, Dr. Berliner agreed with Plaintiffs that:

  • Teachers are the in-school factor with the biggest impact on student learning.
  • All students need to have effective teachers.
  • Ineffective teachers have an adverse impact on students and hurt students’ life chances, regardless of other in-school or out-of-school factors.
  • Standardized test scores are a way to measure students’ progress, and teachers affect students’ achievement on standardized tests.
  • It takes a while for teachers to get good at their jobs, and a probationary period of three to five years would be better than the current probationary period of 18 months.
  • There are some teachers who are consistently ineffective regardless of the students or subjects they teach.
  • Principals do not have difficulty identifying the poorest performing teachers.
  • With multiple years of data, VAM should be able to identify the poorest performing teachers.

Dr. Berliner also confirmed during cross-examination that even if value-added models were perfect and reliable, he would still oppose them.

Defendants’ and Intervenors’ second witness of the day, Ms. Nichols, is an education program consultant employed by the California Department of Education and a former history teacher. Ms. Nichols began testifying about the uneven distribution of credentialed teachers in California, but the Court ruled that line of questioning irrelevant because there has been no evidence that “credentialed” teachers are necessarily effective. Ms. Nichols also testified that as a teacher, she felt comfortable teaching certain topics like Islam, evolution and Catholicism in the classroom because she had tenure. However, during cross-examination, Ms. Nichols conceded that she taught those subjects not because she was exercising “academic freedom,” but because they are part of the state-mandated curriculum.


Expert witnesses for Plaintiffs, including Dr. Raj Chetty, a Professor of Economics at Harvard University and a MacArthur “Genius” award recipient, and Dr. Thomas Kane, a Professor of Education and Economics at the Harvard Graduate School of Education and the Faculty Director of the Harvard Center for Education Policy and Research, testified about the tremendous impact of teachers on students’ long-term academic, social and economic success.

Dr. Raj Chetty:

  • “[T]eacher effectiveness has a profound effect on students’ long-term success as measured by a variety of indicators, such as probabilities of attending college, earnings, teenage pregnancy rates, the neighborhoods where children live as adults and so forth. And so having a highly effective teacher significantly improves children’s outcomes and having a highly infective teacher, conversely, does substantial harm.”
  • “[I]f a child is assigned to a highly effective teacher as measured by their impacts on test scores, it’s not merely that that teacher is effective at teaching to the test and raising student’s performance on tests, but also that that teacher has longer term impacts on outcomes we ultimately care about from education. Like attending college, like earnings, like teenage pregnancy.”
  • “Leaving ineffective teachers in schools reduces the learning of minority and low-income students, as measured by their test scores. It reduces their long term prospects of success, as measured by college attendance, earnings and a variety of other outcomes, and so I think it directly harms low-income and minority students in a variety of ways that have important impacts on their lives.”
  • “[For the] classroom of students taught by the single teacher who is laid off, if you lay off the least-effective teacher, the earnings of the student will rise by, we estimate, $2.1 million. The entire classroom of students over their lifetime would increase by $2.1 million, if you laid off the least-effective teacher instead of the least-experienced teacher.”

bias in value added

Dr. Thomas Kane:

  • “Particularly in teaching, it is very hard to know who the effective and ineffective teachers are going to be at the moment that you recruit them. We know that there are huge differences that emerge later, but it’s hard to know who those teachers are going to be at the moment you recruit them. And so it’s particularly important…to measure performance on the job.”
  • “We learned [from the Measures of Effective Teaching Project] that it is possible to implement systematic and replicable measures of teacher effectiveness, and that the teachers identified as effective using those methods do cause greater student achievement to happen.”
  • “[In conducting the 2013 study on teacher effectiveness in Los Angeles Unified School District,] there were three key findings. First, that teacher effectiveness in LAUSD is measureable and predictable. Second, that the impact on students of being assigned to an ineffective teacher is nearly twice as large in LAUSD than in New York City…Third, that ineffective teachers in Los Angeles are disproportionately assigned…to black and Latino students.”
    • In LAUSD, students assigned to fifth percentile teachers in English Language Arts lose 9.54 months of learning, compared to students assigned to average teachers.
    • In LAUSD, students assigned to fifth percentile teachers in math lose 11.73 months of learning, compared to students assigned to average teachers.
    • “African American students in Los Angeles are 43 percent more likely than white students to be taught by teachers in the bottom 5 percent, and Hispanic or Latino students in LAUSD are 68 percent more likely than white students to be taught by a teacher in the bottom 5 percent.”