The Study That Proves Everything — If You Don't Read It
They sent the email. I read the study. Here is what they left out.
The Study That Proves Everything — If You Don’t Read It
I get emails like this regularly: “Research confirms.” “Study proves.” “Evidence shows.” Most go straight to the trash, but on April 1st, Solution Tree sent one with a particularly bold proclamation: “New study confirms PLC at Work® drives results.” This one I had to read, and I did. All of it, including the methodology section that most people never reach. What I found was not a “landmark study,” but a masterclass in how the education consulting industry operates. They manufacture the appearance of evidence while carefully avoiding the burden of actually producing it. Real evidence is harder to manufacture and considerably less profitable.
I have been down this road before. I subjected Peter Liljedahl and Building Thinking Classrooms to the same scrutiny for precisely the same reason. The product changes. The playbook doesn’t.
What Solution Tree Is Claiming
Here is what the email told me:
Students in PLC at Work schools gained the equivalent of an additional 2.9 months of reading achievement
Students gained the equivalent of an additional 3.4 months of math achievement
Statistically significant gains in both reading and math across all schools studied
In some states, schools achieved up to two years of growth in one year
That last claim — “up to two years of growth in one year” — is the kind of language that ends up in a superintendent’s slide deck before a board vote on a six-figure professional development contract. It is designed to. That number deserves scrutiny. So does the research behind it.
The Study Behind the Claims
The research was conducted by Curtis Jones, Ph.D., through the Office of Socially Responsible Evaluation in Education (SREED) at the University of Wisconsin-Milwaukee, a legitimate institution lending its credibility to a study it did not independently fund. The methodology, in places, is reasonably sophisticated. These details matter because they are precisely what lends this kind of commissioned report its credibility.
The study was commissioned and funded by Solution Tree, the company that owns, sells, and profits from PLC at Work (Jones, 2026). That fact is disclosed on page one of the report. It does not appear anywhere in the marketing email.
That single fact does not make the study fraudulent. It does mean that the financial incentives run in one direction — toward favorable results. It means the study was never subjected to independent peer review before it landed in your inbox. It means not a single independent scholar evaluated whether the conclusions match the evidence before it was sent to your inbox.
Keep that in mind as we proceed.
The Sample: Who Was Actually Studied
This is where the study’s central problem lives, tucked into the methodology section that most readers will never reach.
The 369 schools in this study were not randomly selected. They were not a representative cross-section of American schools. They were schools that Solution Tree itself had already designated as “Model PLC at Work® schools.” To earn that designation, schools had to demonstrate a minimum of three years of sustained implementation along with evidence of ongoing improvement in student achievement.
Read that carefully. Solution Tree hand-picked the schools most likely to show positive results, then paid for a study to confirm it.
The study frames this as a methodological feature rather than a liability: by restricting the sample to high-fidelity implementers, the researchers were examining PLC at Work “under conditions of strong implementation.” What this framing omits is that these schools were already performing at the 66th percentile before the study period began. These were above-average institutions with stable leadership, experienced staff, and the organizational capacity to sustain a multi-year framework implementation. They were not struggling schools desperately searching for solutions. They were already successful schools doing what successful schools tend to do: continue to improve.
There is a term for this in research methodology: selection bias. When a sample is filtered for characteristics associated with success before measurement begins, the results cannot be generalized to schools that don’t share those characteristics. The study does not tell us what happens when an average school, or a struggling school, implements PLC at Work. It tells us what happens when schools that have already demonstrated they can succeed continue to operate. These are fundamentally different questions, and only one of them appears on the cover.
PLC at Work is not being marketed to the 66th percentile. It is being sold to every school that can write a check.
“Independent Research” Is Doing a Lot of Work Here
Solution Tree’s email describes this as “new national research from the University of Wisconsin-Milwaukee.” That framing is deliberate and it deserves scrutiny.
A university affiliation is not the same as independent research. Independent research means the funder has no financial stake in the outcome. It means the findings have been peer-reviewed by scholars with no professional or financial connection to the program. It means other research teams have attempted to replicate the results with independent samples. None of those conditions are met here.
This is the first national study of PLC at Work. The prior studies cited in the report’s discussion section, both conducted in Arkansas and Texas, were also evaluation studies conducted within Solution Tree’s professional development ecosystem (Hanson et al., 2021; Mansell & Kirksey, 2025). There is no independent replication. There is no disclosed peer review. What exists is a university letterhead, a sophisticated-looking methodology section, and a marketing email timed for distribution to school administrators in the spring budget cycle.
What the Email Chose Not to Tell You
Here is the claim featured in Solution Tree’s marketing: schools in some states achieved “up to two years of growth in one year.”
Here is where that number comes from: Kentucky and Missouri reading results, the two highest-performing outliers in a 14-state dataset.
Here is what the marketing email did not mention: Colorado showed no statistically significant gains. Florida showed no statistically significant gains; achievement trended downward. Arkansas showed no statistically significant gains. New York showed no statistically significant gains.
Four out of fourteen states. No significant results. In one state, the trend was negative.
That information is in the study. It is right there in Tables 2 and 3. You have to read past the executive summary, past the discussion section, and into the state-by-state data tables to find it. The marketing email selects the two strongest outliers as the headline and says nothing about the four states where the framework showed no measurable benefit.
This is not an oversight. This is a choice.
What the Numbers Actually Mean
The national math effect size reported in this study is 0.15. The national reading effect size is 0.13.
To interpret those numbers: John Hattie’s widely cited synthesis of educational research uses an effect size of approximately 0.40 as a benchmark for roughly one year of academic learning (Hattie, 2009). The PLC at Work study converts its effect sizes into “months of learning” using this benchmark. That is how 0.15 becomes “3.4 additional months of math learning.”
A genuine gain of three months is meaningful under the right conditions: the effect must be real, caused by the intervention rather than by pre-existing school characteristics, and achievable in schools without the structural advantages present in this sample. But effect sizes of 0.13 and 0.15 are modest. They fall well below what researchers would characterize as a strong effect. And they are being presented alongside language like “proven,” “confirms,” and “landmark” — that implies a level of certainty the data do not support.
There is an important distinction that rarely gets made in faculty meetings: statistical significance is not the same as practical significance. A statistically significant result means the effect is unlikely to be zero. It does not mean the effect is large enough to justify the time, cost, and organizational disruption of a district-wide professional development initiative. That is a question this study does not address and that Solution Tree’s email is not interested in asking.
What This Study Actually Tells Us
Here is the honest summary, without the marketing language:
The national effect amounts to roughly three months of additional learning in reading and math. That finding comes with significant context. These schools were already operating at the 66th percentile before the study began, and were carefully selected by Solution Tree itself. And even among the fourteen states that agreed to participate in the study, four showed no significant improvement whatsoever.
That is what the data say — nothing more.
This study does not establish that PLC at Work is effective for typical schools. It does not demonstrate that PLC at Work outperforms alternative professional development approaches. It cannot disentangle the effects of the framework itself from the broader characteristics of high-functioning schools that have the organizational capacity to sustain it. Nor has it been independently peer-reviewed or replicated by researchers with no financial relationship to Solution Tree.
Why You Need to Know This
I am not writing this to argue that PLC at Work is without value. The collaborative structures at its core may be genuinely useful under the right conditions. However, I cannot determine that from this study, and neither can anyone else. That is precisely the point.
I am writing this because this will happen to you. This study, or one engineered to the same end, will land on a conference room table in your building. Someone with authority will call it research. Someone with a budget will call it justified.
Most of the teachers in that room will not have read the study. Most of them will not know to ask who funded it, how the schools were selected, whether it was peer-reviewed, or what the effect sizes actually mean in practical terms.
This is not unique to Solution Tree. It is a formula, and it has been refined over decades to do one thing well: convert the appearance of evidence into revenue. First, you commission research on your own product. Then you restrict the sample to schools already positioned to succeed. Next, you bury the inconvenient results in data tables no one will read. Finally, you market the outliers as the headline and distribute the press release before anyone reaches the methodology section. The product changes. The playbook doesn’t.
You deserve to walk into that meeting armed. Start with the money: who funded the research, and who profits if the results are favorable? Then look at the sample — were the schools studied anything like yours, or were they hand-picked for success? Ask whether anyone independent ever reviewed the findings before they became a sales pitch. And ask what the effect sizes actually mean in a real classroom, not in a marketing email. Four questions. That is all it takes.
Those questions will not make you popular with vendors or consultants. They will, however, protect your students, your colleagues, and your school from committing time and resources to programs that remain unproven despite what the marketing claims.
The playbook works because most people never read the study. So read the study.
References
Hanson, H., Torres, K., Yoon, S. Y., Merrill, R., Fantz, T., & Velie, Z. (2021). Growing together: Professional Learning Communities at Work generates achievement gains in Arkansas. Education Northwest. https://educationnorthwest.org/sites/default/files/plc-at-work-impact-evaluation.pdf
Hattie, J. (2009). Visible learning: A synthesis of over 800 meta-analyses relating to achievement. Routledge.
Jones, C. (2026, February). National study of Professional Learning Communities at Work. Office of Socially Responsible Evaluation in Education, University of Wisconsin-Milwaukee. Commissioned by Solution Tree.
Mansell, K. E., & Kirksey, J. J. (2025). Exploring the effectiveness of the PLC at Work process in Texas schools: Part 2. Center for Innovative Research in Change, Leadership, and Education, Texas Tech University. https://files.eric.ed.gov/fulltext/ED675138.pdf
Dr. Bill Tozzo has been a mathematics educator for 27 years. He writes about teaching, learning, and the research — or lack thereof — behind the strategies being sold to schools. Find him at The Ruthless Teacher on Substack.