A secret hiding in plain sight?
Academic researchers have advocated for balanced focus on both constrained and unconstrained skills for years.
Note: Unconstrained Kids unpacks, translates, and integrates academic research and data about skill type and the science of skill building to support the improvement of PK-12 reading, writing, and mathematics. Despite important differences, all reading, writing, and math skills can be boiled down to two types–constrained and unconstrained. This post is another in a series that provides an overview of both types of skills. Like everything on this Substack, this post is a work-in-progress. I will make updates as needed. Footnotes and citations are included at the end. Questions, comments, and suggestions are welcome.
First posted: March 7, 2025
Last updated: April 18, 2026
Three big ideas
Constrained skill theory is one of the most influential ideas proposed over the past 20 years among academic researchers in education.
For at least 15 years, academic researchers have called for more explicit focus on building kids’ unconstrained skills to improve reading and math achievement.
Academic researchers to date have proposed consideration of differences between constrained and unconstrained skills have implications for family engagement, Pre-K programs, educational apps, curricula, assessments, and interventions.
An influential idea in education research
A 2014 article in the journal Nature observed that less than 1% of academic papers receive 1,000 or more citations in other academic publications (Van Noorden et al., 2014). Just 100 citations gets a paper in the top 2% overall. According to Google Scholar, the three articles that often get cited for constrained skill theory — Paris (2005), Stahl (2011), and Snow and Matthews (2016) — currently have over 1,300, nearly 100, and 470 citations, respectively. For academics, this is rare air. This signifies the influence that constrained skill theory has achieved among academic researchers over the past 20 years.
Breakthroughs and insights now emerge regularly from the learning sciences. Yet they are slow to make their way into schools, family support systems, and the social consciousness in positive ways. Too often, new findings on how children learn are left to wilt in inaccessible academic journals, contorted by splashy headlines, or too complicated to lead to real policy changes. - Learning Sciences Exchange, New America Foundation
Advocacy for policy and practice change
Academic researchers use the constrained skill framework to advocate for change in classroom instruction and assessment.
Classroom instruction
Stahl (2011): “Teaching constrained skills explicitly and systematically and matching instruction to students’ developmental needs should ensure that the largest portion of the literacy block can be allocated to the more complex unconstrained abilities throughout the elementary years.”
Snow and Matthews (2016): “[M]any prekindergarten through third-grade classrooms, particularly those serving low-income children, still focus on constrained skills, which are easy to teach and easy to test…our schools may be focusing too much on constrained skills—and too little on unconstrained ones—in the early grades.”
Pianta et al. (2021): “The advantages children gain from enrolling in formal pre-K programs are evident, but it will require continued work to ensure that planned large-scale investments in pre-K deliver on their promise to improve children’s learning and development in the long-term. Balancing instruction between more constrained and more unconstrained instruction in pre-K and early elementary school programming — and measuring children’s progress in both types of skills — shows promise for making progress on this goal.”
Whittingham et al. (2024): “When constrained skills (i.e., print-centric skills including alphabetic knowledge and phonics) taught in isolation dominate instructional time, critically important unconstrained skills (i.e., meaning-centric skills including comprehension and composition) and reading-adjacent skills (i.e., interest, motivation) that underlie long-term literacy development are compromised.”
Assessment
Pianta et al. (2021): “Invest in developing a broader set of assessments that capture more unconstrained skills —competencies that are admittedly more difficult to assess — in addition to more constrained skills, which are more typically used by schools and researchers because they are easier to assess and directly aligned with standards.”
McCormick and Mattera (2022): “As investments in publicly funded pre-K expand, policymakers and localities are increasingly looking to use assessments of children’s skills to understand whether programs effectively support learning and development. Recent research examining constrained and unconstrained skills points to the value of expanding the types of skills measured to understand more fully the effects of pre-K on children over time.”
Whittingham et al. (2024): “Whereas assessment and accountability are essential to documenting student growth and proficiency, prioritizing assessments that emphasize constrained skills overestimates a readers’ ability to make sense of text. Instead, they are simply demonstrating accurate decoding…Changing instructional practices to emphasize both constrained and unconstrained skills requires refining and reconceptualizing schools’ assessment systems.”
Hanno et al. (2025): “Overcoming the complexities of capturing unconstrained skills is central to fostering stronger pedagogical practices that build on children's strengths and identifying programs that are most effective in promoting these important skills. One way to deepen domain measurement to include more unconstrained skills is to align assessment content to developmental trajectories rather than focus on discrete skills.”
Research into effects on student achievement
Researchers in recent years published studies about the relationship between constrained and unconstrained skills and student achievement.
Family engagement
McCormick et al. (2020) conducted a correlational study of 307 parents of Pre-K children to evaluate the relationship between constrained and unconstrained learning activities at home and student growth in reading and math. Accounting for a range of child and family variables to isolate the effects of at-home learning, they found extra growth in children’s vocabulary (about 2-3 months) and math problem solving (about 2 months) from increasing unconstrained activities at home from 1-2 times to 3-6 times a week. The gains were greater for families with lower levels of education. Conversely, additional time spent on constrained learning activities at home did not affect these skills.
Classroom
In a study of 470 students and 51 classrooms in Boston Public Schools, researchers (Weiland et al., 2023) found increased exposure during Pre-K to unconstrained language and literacy instruction is a significant predictor of larger learning gains for all students (Maier et al., 2022). While these gains support the potential of high-quality Pre-K instruction to reduce initial disparities in school readiness, research shows that gains in unconstrained skills are significantly more persistent than those in constrained skills (McCormick et al., 2021). However, the long-term impact of these early gains depends on continued high-quality unconstrained instruction in kindergarten and beyond (McCormick et al., 2022).
Interventions
Kim et al. (2021) evaluated 36 studies and nearly 300 outcomes on the effectiveness of educational apps on constrained and unconstrained PK-3 reading and math skills. Controlling for differences between types of assessment and student grade level, they find that education apps make greater gains on constrained skills.1 In fact, the impact is more than twice as large as unconstrained skills.
Thomas et al. (2025) conducted a quasi-experimental study with a literacy-focused educational application (AppLINOU) in 32 schools with just over 500 French students. The research was conducted over two years in Pre-K and kindergarten.2 The study explicitly used the constrained skill framework. The researchers found statistically significant effects for constrained literacy skills (letter knowledge and phonological awareness) but none for unconstrained oral language skills.
High-quality research always comes with careful caveats of the limitations of the studies. The study design also has important relevance. The research design of these studies include random experiments, meta-analysis, and correlational analysis. And some papers more explicitly use the constrained skill framework to test the impact of changes in practice than others. Another challenge is the lack of consistency in definition and frameworks (Chia et al., 2026).
A largely unknown idea in PK-12 education and youth development
Since early 2024, I’ve directly engaged with hundreds of people in PK-12 education and youth development about constrained and unconstrained skills. The bulk of these engagements occurred through presentations and workshops I delivered in late 2025 and early 2026. The people I interacted with are knowledgeable people who are deeply invested in creating brighter futures for children and youth. Many of them are expressly focused on disrupting general poverty through closing the achievement gap. I’ve repeatedly found that educators and practitioners inside and outside of schools had never heard of constrained and unconstrained skills.
This does not appear to be limited to adults working directly with children and youth in schools and out-of-school programs. I pored through reports and webinars in 2024 and 2025 about learning loss in the wake of COVID 19-related school closures. I failed to find any references to skill type in any of these analyses or policy recommendations. Yet, my analysis of national data finds that the decline in reading and math performance was greater for unconstrained than constrained skills.3
This first chart shows proficiency levels of U.S. nine-year-olds eligible for free- and reduced-price meals on the NAEP Long-Term Trend Assessment.4 The chart focuses on constrained math and reading skills, showing proficiency before (early 2020) and after the outbreak of the COVID-19 pandemic. As you can see, there was a relatively small two percentage point decline for math and four percentage points for reading.
By comparison there was no decline for U.S. nine-year olds not eligible for free- and reduced-price meals in schools. (The difference in reading proficiency is not statistically significant.)
The overall decline in reading and math scores was due to lower proficiency in unconstrained math and reading skills. This next chart shows changes in proficiency for different levels of unconstrained math and reading skills for these same cohorts of nine-year-olds in 2020 and 2022. The declines were between 6-8 percentage points — about double those of constrained skills.
In contrast to the lack of change in constrained skill proficiency, U.S. nine-year-olds not eligible for free- and reduced-lunch did experience declines in unconstrained reading and math skills.
Hadley et al. (2025) found similar patterns of the impact of the pandemic on constrained and unconstrained skill in a two-year longitudinal study of Pre-K and kindergarten students. They conclude this difference may be due to the nature of instruction during the pandemic: “Some evidence suggests that instruction during the pandemic, especially remote instruction, may have emphasized discrete, constrained skills such as letter knowledge that could be more easily taught through resources such as apps and worksheets and required scaffolding from adults.”
But wait, there’s more
If you’d like to learn more about constrained and unconstrained skills, check out these other topics:
Works cited
Chia, J., Levickis, P., & McFarland, L. (2026). Unconstrained and Constrained Literacy Skills in Early Childhood Education: A Scoping Review. Australasian Journal of Early Childhood, 18369391261421725.
Hadley, E. B., Liu, S., Kim, E., McKenna, M., & Hull, K. (2025). Tracing the impact of COVID-19 on early language and literacy development from Pre-K through first grade. AERA Open, 11(1), 1–22.
Hanno, E. C., Portilla, X. A., & Hsueh, J. (2025). Designing equity-centered early learning assessments for today’s young children. Child Development Perspectives, 19(2), 92–98.
Kim, J., Gilbert, J., Yu, Q., & Gale, C. (2021). Measures matter: A meta-analysis of the effects of educational apps on preschool to grade 3 children’s literacy and math skills. AERA Open, 7(1), 1-19.
Maier, M. F., McCormick, M. P., Xia, S., Hsueh, J., Weiland, C., Morales, A., Boni, M., Tonachel, M., Sachs, J., & Snow, C. (2022). Content-rich instruction and cognitive demand in prek: Using systematic observations to predict child gains. Early Childhood Research Quarterly, 60, 96–109.
McCormick, M., & Mattera, S. (2022). Learning more by measuring more: Building better evidence on pre-k programs by assessing the full range of children's skills. MDRC: New York, NY.
McCormick, M., Weiland, C., Hsueh, J., Pralica, M., Weissman, A. K., Moffett, L., ... & Sachs, J. (2021). Is skill type the key to the preK fadeout puzzle? Differential associations between enrollment in preK and constrained and unconstrained skills across kindergarten. Child Development, 92(4), e599-e620.
McCormick, M. P., Weissman, A. K., Weiland, C., Hsueh, J., Sachs, J., & Snow, C. (2020). Time well spent: Home learning activities and gains in children’s academic skills in the prekindergarten year. Developmental Psychology, 56(4), 710.
Pianta, R., Purtell, K., McCormick, M., Knoche, L., Burchinal, M., Ludvik, D. & Peisner-Feinberg, E. “Sustaining the pre-k boost: Skills type matters,” Spring (Lincoln, NE: Early Learning Network, 2021).
Snow, C. E., & Matthews, T. J. (2016). Reading and language in the early grades. The Future of Children, 57-74.
Stahl, K. A. D. (2011). Applying new visions of reading development in today's classrooms. The Reading Teacher, 65(1), 52-56.
Thomas, A., Hoareau, L., Jarlégan, A., Hubert, B., Luxembourger, C., & Tazouti, Y. (2025). Enhancing French preschoolers’ early literacy skills with a new educational classroom application. Early Education and Development, 36(4), 886–911.
Van Noorden, R., Maher, B., & Nuzzo, R. (2014). The top 100 papers. Nature, 514, 550-553.
Weiland, C., Moffett, L., Rosada, P. G., Weissman, A., Zhang, K., Maier, M., Snow, C., McCormick, M., Hsueh, J., & Sachs, J. (2023). Learning experiences vary across young children in the same classroom: Evidence from the individualizing student instruction measure in the Boston Public Schools. Early Childhood Research Quarterly, 63, 313–326.
Whittingham, C. E., Hoffman, E. B., & Paciga, K. A. (2024). Assessment, accountability, and access: Constrained skill mastery as instructional gatekeeper. Journal of Early Childhood Literacy, 24(1), 69-95.
Kim et al. (2024) also note that “one-to-one tutoring, small-group instruction, and whole-classroom interventions typically have their largest impact on constrained skills such as letter knowledge, print awareness, and phonemic awareness in literacy and counting, sorting shapes, and simple sums in math.”
The app contained 10 literacy activities that addressed both constrained (phonological awareness and letter knowledge) and unconstrained skills (vocabulary and listening comprehension). Students in experimental classrooms used the app for 20 minutes per week (two 10-minute sessions). Students in control classrooms experienced “business as usual” instruction. The intervention lasted for 10 weeks in the Pre-K year and 15 weeks in the kindergarten year. Teachers were given 10 hours of training but were allowed to integrate use of the app into their classrooms as they saw fit.
This is echoed in Hadley et al. (2025) who found “young children showed especially severe learning loss in unconstrained literacy skills (e.g., comprehension) versus constrained skills (e.g. phonics)” in a longitudinal study of children from Pre-K through first grade.
For details about the NAEP LTT performance levels, see: https://nces.ed.gov/nationsreportcard/ltt/performance-levels.aspx