Corrections log

When this site gets something wrong, the error is corrected on the page where it appeared. Every substantive correction is also recorded here, newest first. Each entry states what was wrong, what was changed, why the error happened and which pages were affected. Where a correction changes a page substantively, that page also carries a short, dated note linking back to this log. The standard behind this practice is set out in section 6 of the editorial policy.

11 October 2026: research findings, census figures, rights and dates

This correction covers a review of the site’s statements about research, schools, rights and history against their sources, and of how the Swedish Plain Language pages described themselves.

What was wrong

1. Research findings were misdescribed. The 132,249 data points in Randolph et al. (2023) were described as participants, and its 2,012 search results as studies screened. Studies using admission lotteries were said to compare families who applied with families who did not, when they compare applicants who were offered a place with applicants who were not. More engaged parents were described as an explanation that lottery studies cannot rule out, although the real limits of such studies are low or uneven consent and missing data. Effect sizes were said to “tend to shrink or disappear” in middle and high school and in public settings, when the 2023 review found them smaller.
2. Claims were stated that this site had not checked. These were that admission-lottery studies were the strongest evidence in the 2023 review; that Angeline Lillard’s research is the field’s most frequently cited source of lottery-based or causal evidence; that the US Department of Education’s clearinghouse had been unable to draw firm conclusions; that the review’s inclusion criteria were a strict bar and a methodological strength; that fees are the single biggest barrier to access; and, on the Training and Certification Pathway Comparison, in this site’s own voice, that AMI training offers the closest available fidelity to Montessori’s own lectures, materials and original design. Montessori’s own account of how a young child takes in a second language was stated as fact.
3. The evidence was summed up in single verdicts. Pages called it “promising”, “increasingly studied with stronger methods than a decade ago” and “well-supported for the early years in particular, promising overall”, called Randolph et al. (2023) the current best synthesis, and described Montessori education on the home page as “reasonably well-supported by a growing evidence base, particularly for early childhood”. This site no longer gives a single verdict of that kind.
4. The 2022 Global Montessori Census was misdescribed. It was presented as a count of verified schools made by direct outreach, set against advocacy-sector estimates of 20,000–22,000. Its figure of around 9% was given as the share of Montessori schools that are publicly funded, without the census’s own definition (fully government funded), without its authors’ note that respondents may have read the funding question in different ways, and sometimes without a source. Public funding was said to be concentrated in three countries, where the census names four, including India. The United States figures were given as roughly 600 publicly funded schools out of an estimated 3,000, where the census cites 579 publicly funded programmes among the 2,728 schools that had taken part in the national Montessori census kept by the National Center for Montessori in the Public Sector.
5. Rights information was out of date or imprecise. The US public-domain rule was given as publication before 1928; as of 1 January 2026 the cut-off is publication in 1930 or earlier. The 1912 translation of The Montessori Method was marked as copyrighted without noting that it is in the US public domain, and the 1913 and 1917 English editions were left unchecked. The Montessori-Pierson Publishing Company was described as operating under AMI’s umbrella, wording that was imprecise and gave no source.
6. The four planes of development were given wrongly in the Glossary as 0–3, 3–6, 6–12 and 12–18. Montessori’s four planes are 0–6, 6–12, 12–18 and 18–24; 0–3 and 3–6 are the two halves of the first plane.
7. Pages for children stated unchecked facts. Who Was Maria Montessori? said that she lived “well into her eighties”; she died in 1952, aged 81. It also said that there are Montessori classrooms on every continent, which this site had not checked. The Story of Everything said that people invented ways of counting “at around the same time” as writing, and that the reader’s teachers think it is one of the best stories there is, neither of which this site had checked. Several pages for children also presented Maria Montessori’s beliefs, and common Montessori practice, as facts about all children or all Montessori classrooms.
8. In the Swedish edition only, Montessori at Home suggested cooking with a knife described as “slipad (ej vass)” for children aged 3 to 6, and its Plain Language edition with a “slipad” knife. “Slipad” means sharpened, so the first wording contradicted itself, and both could be read as advice to give a child a sharp knife. The English versions have always said a blunt knife.
9. In the Swedish edition only, the Plain Language pages said that they were written to the guidelines of MTM (Myndigheten för tillgängliga medier, the Swedish government agency for accessible media). The short descriptions these pages give to search engines and link previews read “Skriven enligt MTMs riktlinjer för lättläst” (“Written according to MTM’s guidelines for easy-to-read text”). No readability measurement backed that claim, so this site could not show that the pages meet those guidelines. The English Plain Language pages have never claimed to follow any guidelines.

What was changed

• Each description of a study now matches its published text: data points, search results and what a lottery compares are stated correctly, and the 2023 review is described as finding smaller effects in those settings.
• Claims this site had not checked have been removed. The training page now gives AMI’s own description of its training, quoted with a dated source, and says that this site has not reviewed evidence on whether the training route affects classroom fidelity or children’s outcomes. Montessori’s account of second-language learning is now attributed to her.
• Single verdicts have been replaced with an attributed, outcome-by-outcome account. Two syntheses published in 2023 reported positive average effects. A national lottery-based trial published in 2025 found effects at the end of kindergarten (ages five to six) on some outcomes and not on others, with its limits stated. A 2026 review found large pooled effects but judged them not robust.
• The census is now described with its own definition, its authors’ caveats and its own figures, and the source of the 9% figure is named.
• The Historical Timeline gives the current US public-domain rule, the US status of the 1912 translation and, with a dated source, the Montessori-Pierson Publishing Company’s own description of its relationship to AMI.
• The Glossary gives the four planes as 0–6, 6–12, 12–18 and 18–24.
• The pages for children give Maria Montessori’s dates correctly, no longer make the unchecked claims, and say where they describe her beliefs or the Montessori approach rather than established facts.
• The Swedish Montessori at Home and its Plain Language edition now say a blunt knife (“trubbig kniv”), as the English versions do.
• The Swedish Plain Language pages now describe themselves as “Skriven på lättläst svenska” (“Written in easy-to-read Swedish”), in line with the English pages’ “Written in plain language”, and no longer name MTM’s guidelines.
• Pages whose content changed substantively now carry a dated correction note linking to this log.

Why it happened

These statements were not checked against their sources, or against the current state of the site, before publication. The Swedish knife wording was a translation error. The claim that the Swedish Plain Language pages follow MTM’s guidelines was published before any readability measurement had been made to support it, and no such measurement has been made yet.

Pages affected

• Understanding the Stages and its Plain Language edition: research findings, unchecked claims and a single verdict.
• FAQ and Myth-Busting and its Plain Language edition: the census figure, the claim about fees and a single verdict.
• Glossary and its Plain Language edition: the four planes.
• Evidence Status: research findings, unchecked claims, the census and a single verdict.
• Annotated Bibliography: research findings, unchecked claims and the census.
• International Comparative Data: the census and its figures.
• Historical Timeline: rights information.
• Editorial Policy, section 1: the same wording about the Montessori-Pierson Publishing Company, now pointing to the Historical Timeline.
• Training and Certification Pathway Comparison: an unchecked claim about AMI training.
• Who Was Maria Montessori?: dates, an unchecked claim and beliefs stated as facts.
• The Story of Everything: unchecked claims and an idea stated as fact.
• Montessori i hemmet and its lättläst version (Swedish edition only): the knife.
• The Swedish Plain Language pages För vårdnadshavare, Att förstå utvecklingsstadierna, Att välja en skola, Montessori i hemmet, Vanliga frågor och myter, Ordlista and Vidare läsning (Swedish edition only): the claim about MTM’s guidelines, in the page description only.
• Home page: framing only.
• A Day in a Montessori Classroom, Activities to Try, Why Real Things, Not Toys? and Why Different Ages Are Together: framing only.

10 October 2026: citation and description of León et al. (2026)

This correction concerns a 2026 review of the evidence on Montessori education:

León, S.P., Lipnevich, A.A. and García-Garrido, M. (2026), “The Montessori Method Under Scrutiny: A Meta-Analytic and Metascientific Review for Greater Transparency in Education Research,” Review of Educational Research, published online 7 July 2026, https://doi.org/10.3102/00346543261458396.

What was wrong

1. The citation was wrong. It gave the wrong initials for two of the three authors (“León, A.M.” and “García-Garrido, M.D.”; the authors are Samuel P. León and María García-Garrido) and had no DOI.
2. The review was described as re-examining the earlier studies. Several sentences said it drew on “the same body of studies”, “substantially the same body of primary studies” or “substantially the same primary-study pool” as the 2023 Campbell review by Randolph et al., referred to researchers “studying the same data”, or called the disagreement a dispute “over the same underlying data”. Nothing this site has verified supports that. How far the two reviews draw on the same studies is not known to this site.
3. Claims were attributed to the review that are not in its published abstract, which is the only part of it this site has verified. These were that the pooled effects in the earlier reviews are “substantially inflated”; that neither earlier review disclosed its search strategy transparently enough to rule this out; and that the review raises a concern about researchers’ independence of the same kind as the co-authorship point this site had noted about the Campbell review.
4. The review was framed as aimed at one earlier synthesis. Phrases such as “A direct, unresolved challenge to that synthesis”, “dispute over the field’s strongest existing synthesis” and “challenged the 2023 Campbell review” implied that the review targeted Randolph et al. (2023) specifically. Nothing in the verified record shows that.
5. The 2023 review was called the most substantial recent synthesis. On Understanding the Stages and its Plain Language edition, Randolph et al. (2023), a review of 32 studies, was described as “the most substantial recent” synthesis directly before the description of a 2026 review that identified 198 studies.

What was changed

• The citation now gives the correct authors, the title exactly as published, the date of online publication and the DOI, as above.
• Statements that the two reviews used the same studies or the same data have been removed. Where it is relevant, pages now name the open questions instead: how far the two reviews’ study pools overlap, and whether either review’s estimates hold up under the other’s checks for bias.
• Claims that are not in the published abstract have been withdrawn. Because this site has not yet read the full text, the review is now described from its abstract only. It is a preregistered systematic review and meta-analysis that identified 198 studies, 114 of them with enough data for meta-analysis. It found “nominally positive and conventionally large” pooled effects on learning outcomes in pretest–posttest and posttest-only designs, but judged those estimates not robust: they showed extreme between-study heterogeneity, substantial small-study effects and clear signs of publication bias, and inconsistent reporting of implementation fidelity, low transparency and limited experimental control further limited how far they generalise. The authors conclude that the large average effects reported in the literature are “largely attributable to structural weaknesses of the evidence base rather than to robust educational impacts”. The review does not conclude that Montessori education has no effect.
• The disagreement is now framed neutrally. A 2026 review reaches a sharply different conclusion about the Montessori evidence base from the 2023 syntheses (Randolph et al. 2023; Demangeon et al. 2023), and researchers currently disagree about how strong that evidence is. The pages still say plainly that this disagreement is live and unresolved.
• Understanding the Stages and its Plain Language edition now describe Randolph et al. (2023) as one major recent synthesis.
• Pages whose description of the review changed substantively now carry a dated correction note linking to this log.
• Section 6 of the editorial policy previously said that corrections are recorded in the commit history, which readers cannot see. It now points to this log.

Why it happened

The citation and the description of the review were not checked against the publisher’s record before publication.

Pages affected

• Evidence Status: citation, description and framing.
• Annotated Bibliography: citation, description and framing.
• Understanding the Stages: citation, description and framing.
• Understanding the Stages (Plain Language edition): citation, description and framing.
• Home page: framing only.
• For Researchers: framing only.
• FAQ and Myth-Busting: framing only.
• FAQ and Myth-Busting (Plain Language edition): framing only.
• Editorial Policy, sections 3 and 6: framing only. Section 6 also now points to this log instead of the commit history.