About

Thomas S. Dee, Ph.D., is the Barnett Family Professor at Stanford University’s Graduate School of Education, the Robert and Marion Oster Fellow at the Hoover Institution, and a Senior Fellow at the Stanford Institute for Economic Policy Research (SIEPR). He is also a Research Associate at the National Bureau of Economic Research (NBER) and the Faculty Director of the John W. Gardner Center for Youth and Their Communities. His research focuses largely on the use of quantitative methods to inform contemporary issues of public policy and practice. Dee has received notable awards including the Peter H. Rossi Award for Contributions to the Theory or Practice of Program Evaluation from the Association for Public Policy Analysis and Management (APPAM) and the Outstanding Public Communication of Education Research Award from the American Educational Research Association (AERA). His work has addressed topics such as the impact of immigration raids on student attendance, the effects of school cell phone bans, and the consequences of immigration enforcement on student achievement. Dee's research is widely recognized and frequently cited in media outlets, reflecting his significant contributions to education policy and public policy research.

Research topics

• Political Science
• Sociology
• Medicine
• Psychology
• Demographic economics
• Demography
• Medical education
• Mathematics education
• Economics
• Economic growth
• Socioeconomics
• Pedagogy
• Geography

Selected publications

• Accelerating Opportunity: The Effects of Instructionally Supported Detracking

  American Educational Research Journal · 2026-01-28

  article1st author

  The pivotal role of algebra in the educational trajectories of U.S. students continues to motivate high-profile policies focused on when students access the course, their peers, and how it is taught. This random-assignment partnership study examined an innovative district-level reform—the Algebra I Initiative—that placed ninth grade students with prior math scores below grade level into Algebra I classes coupled with teacher training instead of a remedial pre-algebra class. We found that this reform significantly increased grade 11 math achievement (extreme spread = 0.2 SD) without lowering the achievement of classroom peers. This initiative also increased attendance and district retention. These results suggest that higher expectations for the lowest-performing students coupled with aligned teacher supports is a promising model for realizing students’ mathematical potential.

  PublisherDOI

• Ahead of the Game? Course-Taking Patterns Under a Math Pathways Reform

  Educational Researcher · 2025-01-02 · 3 citations

  articleSenior author

  A controversial, equity-focused mathematics reform in the San Francisco Unified School District (SFUSD) featured delaying Algebra I until ninth grade for all students. This study examines student-level longitudinal data on mathematics course-taking across successive cohorts of SFUSD students who spanned the reform’s implementation. We observe large changes in ninth and 10th grades (e.g., delaying Algebra I and geometry). Participation in Advanced Placement (AP) math initially fell 15% (6 percentage points), driven by declines in AP calculus and among Asian/Pacific Islander students. However, growing participation in acceleration options attenuated these reductions. Large ethnoracial gaps in advanced math course-taking remained.

  PublisherDOI

• Emergency mental health co-responders reduce involuntary psychiatric detentions in the USA

  Nature Human Behaviour · 2025-11-17

  articleOpen access1st authorCorresponding

  Historical efforts to deinstitutionalize those experiencing mental illness in the USA have inadvertently positioned police officers as the typical first responders to emergency calls involving mental health crises and empower them to initiate involuntary psychiatric detentions. Although potentially lifesaving, such detentions are controversial and costly, and they may be medically inappropriate for some of those detained. Here we present evidence from two quasi-experimental designs on the causal effects of a ‘co-responder’ programme that pairs mental health professionals with police officers as first responders on qualified emergency calls. The results indicate that a co-responder programme reduced the frequency of involuntary psychiatric detentions by 16.5% (that is, 370 fewer detentions over 2 years; b = −0.180, 95% confidence interval −0.325 to −0.034) but had no detectable effect on programme-related calls for service, criminal offences or arrests. Complementary results based on incident-level data suggest this reduction reflects both a co-responder’s influence on the disposition of an individual incident and a reduction in future mental health emergencies. In a quasi-experimental analysis of emergency calls in California communities, Dee and Pyne find that having mental health first responders accompany police on qualified calls reduces the number of individuals placed in involuntary psychiatric detentions.

  PublisherOA PDFDOI

• Recent immigration raids increased student absences

  Proceedings of the National Academy of Sciences · 2025-11-04 · 3 citations

  articleOpen access1st authorCorresponding

  Local immigration raids expanded dramatically across the United States during the first 2 mo of 2025. Anecdotal accounts suggest that these raids increased student absences from schools because parents fear being separated from their children. This study evaluates this claim using a daily time series of school absences spanning the current and two prior school years from five school districts serving communities subject to recent and unexpected raids in California's Central Valley. The results indicate that recent raids coincided with a 22 percent increase in daily student absences with particularly large increases among the youngest students. These increased absences underscore the broader policy relevance of this immigration enforcement in terms of their impact on schools, childhood stress, and opportunities to learn.

  PublisherOA PDFDOI

• New Advanced Placement course designed to broaden access promotes participation and demographic diversity in computer science education

  Proceedings of the National Academy of Sciences · 2025-04-10 · 2 citations

  articleOpen accessSenior author

  Advanced Placement (AP) provides college-level courses to over 1 million US secondary students annually. Black, Hispanic, and female students have historically been underrepresented in AP Computer Science (CS). A new, broadly focused course-AP CS Principles-launched nationally in 2016-17 with the goal of increasing student participation and diversity. We examine its effects on AP CS participation. Combining publicly available sources, we assemble a panel dataset of annual AP exam-taking and course offerings from 2006-07 to 2020-21 at Massachusetts high schools. Using synthetic difference-in-differences, we estimate that offering the new course led to 16 additional yearly AP Computer Science exams per school, more than tripling baseline exam counts for the average adopting school. Exam counts among female and Black or Hispanic students more than quadrupled. The new exams were concentrated in AP Computer Science Principles, with no statistically significant reduction in exam counts for the preexisting AP CS course. We also estimate that offering the new course increased schools' probability of having any AP CS exam participation by 29 percentage points, with larger gains for female and Black or Hispanic students. We find some evidence of positive spillover effects on several other AP courses. The results suggest the promise of course design and availability in promoting engagement and diversity in advanced STEM education.

  PublisherOA PDFDOI

• The Achievement Effects of Scaling Early Literacy Reforms

  Educational Evaluation and Policy Analysis · 2025-08-21 · 2 citations

  articleSenior author

  While legislators have implemented many “science of reading” initiatives in the last 2 decades, the evidence on the impact of these reforms at scale is limited. In this pre-registered, quasi-experimental study, we examine California’s recent initiative to improve early literacy across the state’s lowest-performing schools. The Early Literacy Support Block Grant (ELSBG) provided teacher professional development grounded in the science of reading as well as aligned supports (e.g., assessments and interventions), new funding (about $1,000 per student), spending flexibility within specified guidelines, and expert facilitation and oversight of school-based planning. Our preferred specification finds that ELSBG generated significant (and cost-effective) improvements in English Language Arts (ELA) achievement in its first years of implementation (0.14 standard deviation) as well as smaller improvements in math.

  PublisherDOI

• The Case for Preregistering Quasi-Experimental Program and Policy Evaluations

  Evaluation Review · 2025-03-12 · 4 citations

  editorialOpen access1st authorCorresponding

  The recognition that researcher discretion coupled with unconscious biases and motivated reasoning sometimes leads to false findings ("p-hacking") led to the broad embrace of study preregistration and other open-science practices in experimental research. Paradoxically, the preregistration of quasi-experimental studies remains uncommon although such studies involve far more discretionary decisions and are the most prevalent approach to making causal claims in the social sciences. I discuss several forms of recent empirical evidence indicating that questionable research practices contribute to the comparative unreliability of quasi-experimental research and advocate for adopting the preregistration of such studies. The implementation of this recommendation would benefit from further consideration of key design details (e.g., how to balance data cleaning with credible preregistration) and a shift in research norms to allow for appropriately nuanced sensemaking across prespecified, confirmatory results and other exploratory findings.

  PublisherOA PDFDOI

• Higher chronic absenteeism threatens academic recovery from the COVID-19 pandemic

  Proceedings of the National Academy of Sciences · 2024-01-09 · 72 citations

  articleOpen access1st authorCorresponding

  The broad and substantial educational harm caused by the COVID-19 pandemic has motivated large federal, state, and local investments in academic recovery. However, the success of these efforts depends in part on students’ regular school attendance. Using state-level data, I show that the rate of chronic absenteeism among US public-school students grew substantially as students returned to in-person instruction. Specifically, between the 2018–2019 and 2021–2022 school years, the share of students chronically absent grew by 13.5 percentage points—a 91-percent increase that implies an additional 6.5 million students are now chronically absent. State-level increases in chronic absenteeism are positively associated with the prevalence of school closures during the 2020–2021 school year. However, these increases do not appear to be associated with enrollment loss, COVID-19 case rates, school masking policies, or declines in youth mental health. This evidence indicates that the barriers to learning implied by the sharp increase in chronic absenteeism merit further scrutiny and policy responses.

  PublisherOA PDFDOI

• No one-size-fits-all solution to chronic absenteeism

  Phi Delta Kappan · 2024-10-28 · 3 citations

  article1st authorCorresponding

  As chronic absenteeism fails to ease from post-pandemic high levels, schools can turn to many reforms to promote school attendance. Commonly recommended strategies involve increasingly targeted and intensive tiers of interventions. Researcher Thomas S. Dee writes that the research base of many of these interventions is not strong. Schools facing financial and capacity restraints may have difficulty putting interventions in place. Dee suggests that educators obtain information on attendance barriers in their schools and base solutions on those data. Sharing information about attendance with families is one promising intervention.

  PublisherDOI

• Quantifying the Effects of Advanced Placement Computer Science Principles on Participation and Diversity in AP CS

  2024-03-14 · 1 citations

  articleSenior author

  We estimate the causal impacts of a new Advanced Placement (AP) course on participation in CS education. AP offers college-level courses, exams, and potentially college credit to U.S. secondary students. Historically, female, Black, and Hispanic students have been significantly underrepresented in AP Computer Science. A new course, CS Principles, was launched in 2016-17 to attract a more diverse group of students. Compared to the Java-focused preexisting course, CS A, CS Principles features a broader framing of CS, a creative project component in assessment, and flexibility for teachers in choosing programming languages. We assemble a dataset of annual AP exam-taking and course offerings at 294 schools in Massachusetts over fifteen years, using publicly available data from the Massachusetts education department and the College Board. Using an interactive fixed effects counterfactual estimator, we estimate that offering CS Principles increased a school's chance of having any students take AP CS exams by 25 percentage points and its count of CS exams by 24. Gains were larger for Black and Hispanic and female students. Offering CS Principles had some negative effects on CS A participation but not on other AP STEM exams. Our preliminary results suggest that elements of the CS Principles launch, including course design, curriculum development, marketing, and teacher training, can inspire other large-scale initiatives promoting engagement and diversity in STEM education. In this Lightning Talk, we hope to share our results and connect with potential collaborators interested in quantitative policy analysis in CS education.

  PublisherDOI

Frequent coauthors

• Brian Jacob

  University of Michigan–Ann Arbor

  39 shared

• Silvie Colman

  Colman Hospital

  34 shared

• James Wyckoff

  University of Virginia

  32 shared

• Theodore Joyce

  29 shared

• Scott Latham

  22 shared

• Daphna Bassok

  22 shared

• Emily K. Penner

  University of California, Irvine

  18 shared

• Veronica Katz

  University of Virginia

  15 shared

Education

• Ph.D., Education

  Stanford University

• M.A., Education

  Stanford University

• B.A., Education

  Stanford University

Awards & honors

• Peter H. Rossi Award for Contributions to the Theory or Prac…
• Outstanding Public Communication of Education Research Award…