The Merits of Watching the Grass Grow: How Longitudinal Studies Bear Real Fruit

Anne looks at the NWEA test results for her second graders.  They seem low, especially when compared to their scores in previous years.  Her students had decent NWEA reading and math scores in kindergarten, but last year and this year the scores seem a bit below her students’ usual performance.  She isn’t sure why though.  She has been teaching second grade for years, but since the pandemic, her students have struggled.  Something is different, but she isn’t sure what it is or how to address it.  Anne is not alone in her confusion.  NWEA recently analyzed their reading and math assessment scores for children in kindergarten, first-grade, and second-grade.  They found that while kindergarteners seem to be performing as usual, first and second graders are scoring below pre-pandemic levels¹. The Early Childhood Longitudinal Study, Kindergarten Class of 2024 (ECLS-K:2024) was designed to follow Anne’s current second graders from kindergarten entry through third grade, collecting information on all sorts of things in and out of school that could influence children’s learning and explain NWEA’s findings. Unfortunately, the ECLS-K:2024 was cancelled last year due to costs.

For decades, the National Center for Education Statistics (NCES), a research arm of the U.S. Department of Education has conducted nationally representative longitudinal studies that follow students over time. Congress asked that NCES conduct these studies because they needed reliable information on how students are doing, what supports students, teachers, and schools need, and how policies are shaping student experiences and outcomes. By following the same students over several years, NCES gives Congress, states, and school districts a clear picture of how different groups of students are doing as conditions change. This long‑term data helps leaders understand what’s working and decide where extra support or resources might be needed.

In the post‑pandemic period, when schools are navigating rapid shifts in technology use, attendance patterns, and student needs, this kind of long‑term, nationally representative information is especially important. Without it, policymakers and educators have a far less complete picture of how to respond to new challenges and sustain high‑quality learning opportunities for all students.

How Longitudinal Studies Track Growth

Longitudinal studies are unique in that the same group of people are assessed at each study time point.  For example, the kindergarteners that participated in the Early Childhood Longitudinal Study, Class of 2010-11, also participated when they were in first, second, third, fourth, and fifth grade.  Because it was the same students at each time point in the study, it is possible to look at short term and long term effects of educational experiences in kindergarten. When the sample is nationally representative, researchers can look at the impact of different factors on different types of students throughout the U.S. over time and identify some of the experiences or skills that account for differences between students once they get to fifth grade. 

Because it is costly to keep track of people over time as they move or change schools, researchers sometimes choose to repeat a study with a new group. Recruiting a new sample of people could be less expensive than tracking people, but any changes you see from the first study time point to the second may be due to the new sample, not a change due to experiences captured at time one. Longitudinal studies ensure that differences are due to experiences, since the people remain the same.

Longitudinal studies take time to complete. It may be years before patterns emerge.  Yet, the findings are worth the wait.  That is, longitudinal studies allow us to identify possible causes of certain outcomes.  For example, we can gain a true understanding of whether ninth graders’ educational expectations relate to their later job and career choices.  Longitudinal data can also suggest which types of students benefit from pull-out services and which ones do not.  Longitudinal studies also reveal what other factors might influence the success or failure of a program or intervention.

How NCES Takes the Long View in Federal Data

NCES, within the Institute of Education Sciences, has invested in longitudinal cohort studies to show lawmakers and educators how students move through the education system and how schools prepare them for college, careers, and lifelong learning.  These cohort studies were often repeated to examine how changes in school programs, technology, and policies influenced children’s school experiences and readiness for the workforce.  NCES longitudinal studies take a comprehensive look at the factors that shape children’s well‑being and learning, spanning influences from home experiences to classroom and school environments.

The NCES longitudinal studies include children from kindergarten through high school and beyond.  The Early Childhood Longitudinal Studies (ECLS) begins with a nationally representative group of kindergarteners and follows them through fifth grade. The Middle Grades Longitudinal Study (MGLS:2017) begins with a nationally representative sample of sixth graders and revisits them again in eighth grade.  Over several decades, NCES has carried out several major longitudinal studies of high school students, including six cohorts beginning with the National Longitudinal Study of the High School Class of 1972 to the most recent High School & Beyond of 2022 to track students’ educational experiences and long‑term outcomes over time. For example, the High School Longitudinal Study of 2009 follows a national group of students who started 9th grade in 2009 to understand their paths through high school, college, and early careers. It pays special attention to what leads students to pursue and stick with STEM courses and careers, with several follow‑up surveys through 2016 and postsecondary transcript collections through 2021.

Early Childhood Longitudinal Study

The first ECLS conducted was launched in 1998 to provide a picture of what students entering kindergarten looked like in terms of their skills and characteristics. The study was also meant to describe how these children moved through elementary school with respect to the skills and competencies they gained. Particular attention was spent on describing how these children moved from grade to grade.  Because the study was longitudinal, and the same children participated at each time point, the study allowed researchers and policymakers to explore how a wide variety of child, family, school, classroom, before and after care, teacher and school characteristics relate to children’s school performance.

Each time this study was repeated, study staff updated the questions asked of participants to ensure that useful information would be collected.  As older topics lost relevance, they were phased out and replaced with questions on current issues such as virtual learning, technology, and new approaches to teaching and learning.  The most recent ECLS, the ECLS-K:2024 was poised to collect information on children who were babies during the pandemic, were less likely to have gone to preschool, and, due to the pandemic, had different home learning experiences than children before the pandemic. The ECLS-K:2024 collected information about the skills these pandemic babies brought to kindergarten and planned to track their achievement as they moved through elementary school.  Unfortunately, the ECLS-K:2024 was cancelled in 2025, just before they revisited students in first grade. 

Middle Grades Longitudinal Study

In 2017, NCES addressed a gap in its mapping of children’s progression from kindergarten to high school graduation and beyond with the MGLS:2017.  That is, there has been ample study of children’s early school experiences as well as of high school students.  Yet, little research has been done on the years in between, despite the growth and development that occurs during the ages of 10 to 14 years.  Following students between elementary and high school allows researchers to better understand how experiences in and out of school influence students’ reading, math, socioemotional well‑being, and general development, offering insight into the foundations of their high school performance. The MGLS:2017 is unique because it followed the same group of students from grade six to eight, tracking their growth in math and reading, along with skills like attention, memory, and social development. It also included enough students with disabilities, including autism and learning disabilities, to study their experiences separately and compare them with general education students. The MGLS:2017 captures how students change over the middle grades and how growth differs across groups and school settings.  Other adolescent education studies either start later, focus on smaller or older samples, or are outdated, so they do not reflect the current experiences of U.S. middle school students². Perhaps most importantly, the COVID pandemic occurred in the middle of the MGLS:2017, forcing the study to pivot to completely virtual data collection.  This pivot allows researchers and policymakers to examine the impact of the pandemic and virtual learning on preadolescents in real time. 

High School Longitudinal Studies

For decades, NCES has run major studies that follow the same high school students over time to understand how their education shapes their lives.  These long‑term studies track students from high school into adulthood, looking at issues like staying in school, graduating, going to college, moving into the workforce, and entering STEM fields. Together, this body of work has helped policymakers and researchers see long‑term trends, understand how student, family, and school experiences are connected, and improve how education research is designed and conducted.

High School and Beyond 2022 (HS&B:22) was the most recent high school longitudinal study conducted by NCES and the first after the COVID pandemic. HS&B:22 was designed to follow a nationally representative group of students who began ninth grade in 2022 as they moved through high school. The study aimed to collect information from students, parents, teachers, and schools to understand students’ coursework, achievement, school experiences, aspirations, and plans for life after graduation. It also planned to link survey data with high school transcripts to provide a fuller picture of students’ academic pathways and how family, school, and personal factors shape their outcomes. Like earlier NCES high school studies, its goal was to show how students’ experiences and decisions unfold over time, rather than at a single moment. In 2025, however, the federal high school longitudinal studies program was canceled, and the planned 12th grade data collection for HS&B:22 was not completed. Without this data collection, it is not possible to examine how well these post-pandemic high school students fared in high school or transitioned from high school to college or the workforce. For example, this cohort of students’ expectations to attain a bachelor’s degree were lower in 2022 than compared to students in the 2009 or 2002 cohorts³.

The High School Longitudinal Study of 2009 followed a nationally representative group of students from the start of ninth grade into early adulthood to understand how their high school experiences shaped their education, careers, and life outcomes. The study collected detailed information from students, parents, teachers, counselors, and schools, with a strong focus on course‑taking, transitions after high school, and pathways into college, work, and STEM fields. As of fall 2024, NCES planned a third follow‑up in 2025 to gather new data on civic participation, family formation, and labor market outcomes, when many participants would have been around 30 years old. However, the federal high school longitudinal studies program was canceled in 2025, and this final follow‑up was never conducted, leaving a significant gap in what the study could reveal about participants’ later adult lives.

How Longitudinal Data Seed Better Policy Decisions

Congress, at one time or another, asked the Department of Education to conduct these longitudinal studies in order to guide policy and funding investments.  The information collected was also made available to the public, allowing for anyone interested to examine pressing issues.  For example, when a few states moved to full-day kindergarten, there was some concern that the longer, more academic day was harmful to young children.  The ECLS-K data was used to compare children in full-day kindergarten to their counterparts in half-day programs, finding benefits for both children and mothers in full-day kindergarten, though these benefits faded out by third grade⁴.  This research helped to convince other states and districts to move to full-day kindergarten programs. 

Researchers and policy makers have also turned to the longitudinal high school studies to examine a whole host of issues to inform policy and funding decisions.  In fact, an examination of research using the HSLS:09 found that its data had been used to inform research across a number of policy issues as it was designed to do⁵.

Additionally, the high school longitudinal studies shed light on the ways in which high schools can prepare students for success in college.  For example, the HSLS:09 found a relationship between math classes taken in high school and success in college math classes⁶. These findings inform high school graduation requirements. It also impacts high school offerings as the HSLS:09 also found that students that took more than three CTE courses in high school later had lower unemployment rates and were more likely to have health and retirement benefits than their peers who took fewer credits⁷.

Classrooms and students have changed as a result of the pandemic and technological advances.  We need these longitudinal studies to understand the impact of these changes. The skills that students need for a successful career are rapidly changing as our post-pandemic world moves towards greater technology dependence.  Teaching practices and education policies need to shift to continue to support a successful workforce. For example, education longitudinal studies could be used to examine the impact of AI and increased exposure to screens on students and their skill acquisition. This understanding ensures funding decisions and policies are effective.

Long-Term Learning Bears Fruit for the Field

Anne is left struggling to figure out how best to help her second-grade students master reading and math. She and her fellow teachers will put their heads together and try some things.  Some of them might work, but some will turn out to be a waste of time.  Longitudinal education studies remove the guesswork.  Following the same students as they move through school, especially in large national samples, allows us to identify the factors that need to be addressed.  One unique aspect of longitudinal studies is that each time they gather information, they build on what is already known.  This means that longitudinal studies tend to have more information on a whole host of topics than a one-time survey⁸, increasing the ability to identify the determinants of an issue, such as the declining reading and math scores among today’s first- and second-graders. Longitudinal studies take time and patience to cultivate, but the yields are more than worth it.

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1. Sullivan, E. T. (2026, March 17). Kids Who Were Babies During COVID Are Now Struggling With Reading and Math. The74million.org. https://www.the74million.org/zero2eight/kids-who-were-babies-during-covid-are-now-struggling-with-reading-and-math/ ↩︎
2.  National Center for Education Statistics. (2017, revised 2018). Supporting Statement Part A: Middle Grades Longitudinal Study of 2017–18 (MGLS:2017) Main Study Design Revision, Operational Field Test First Follow-up (OFT2) and Second Follow-up (OFT3), and Main Study Base Year (MS1) and Tracking for First Follow-up (MS2) (OMB No. 1850‑0911, Version 20). U.S. Department of Education, Institute of Education Sciences. ↩︎
3. Simone, S., & Christopher. (n.d.). Future Education Expectations of High School Students Decline to the Lowest Level in 20 Years for Both First-Generation and Continuing Generation Students. https://www.pellinstitute.org/wp-content/uploads/2025/09/PELL_Educational-Expectations-of-First-Gen-Students_Research-Brief.pdf ↩︎
4. Cannon, J. S., Jacknowitz, A., & Painter, G. (2006). Is full better than half? Examining the longitudinal effects of full-day kindergarten attendance. Journal of Policy Analysis and Management, 25(2), 299–321. https://doi.org/10.1002/pam.20174
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5. Russell, S. L., & Zhang, Y. (2018, August). Review of the research: High School Longitudinal Study of 2009 (HSLS:09) [Poster presentation]. American Psychological Association Annual Convention. American Institutes for Research. ↩︎
6. High school graduates often need remediation in college. (n.d.). https://nces.ed.gov/surveys/hsls09/pdf/college_readiness_508compliant.pdf ↩︎
7.  Labor Market Outcomes for high school career and technical education participants: 2016. (n.d.). https://nces.ed.gov/pubs2020/2020060/index.asp ↩︎
8. Closer. (2020). Learning Hub | Strengths of longitudinal data. Closer.ac.uk. https://learning.closer.ac.uk/learning-modules/introduction/what-can-longitudinal-studies-show-us/strengths-of-longitudinal-studies/
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