Spelling Mastery has potentially positive effects on writing for students with learning disabilities, based on two RCTs with a small extent of evidence¶
Claim · All claims
Evidence · 1 study · quant-synthesisr2·q3·i2medium
Currency · newest study 2014 · checked against its sources 2026-10-20 (automated, 1 of 1 entry) · not reviewed by a person
Subclaims¶
Reading the evidence codes
q is the design tier, i the impact, n the sample, and the kind with its r
the rigour judged within that kind: what each code means.
This claim: no standardized effect is recorded in observations/ for it yet, so no benchmark reading is possible.
q3 i2 Across two RCTs meeting WWC standards without reservations, Spelling Mastery showed a statistically significant positive effect in one study and substantively important positive effects in the other, yielding a domain-average effect size of 0.85 and an improvement index of +30 percentile points. → wwc-summary-1
Evidence¶
wwc-summary-1¶
U.S. Department of Education, Institute of Education Sciences, What Works Clearinghouse. (2014, January). Students with Learning Disabilities intervention report: Spelling Mastery. Retrieved from https://ies.ed.gov/ncee/wwc/InterventionReport/579
q3 · i2 · quant-synthesis · r2
WWC synthesis of two randomized controlled trials (Darch & Simpson, 1990; Darch et al., 2006) totaling 70 students with learning disabilities in grades 2–4. The report states "one study found a statistically significant positive effect and one study found substantively important positive effects," producing the potentially positive effects rating. Appendix C prints a domain average effect size of 0.85 and improvement index of +30.
"Thus, for the writing domain, one study found a statistically significant positive effect and one study found substantively important positive effects. This results in a rating of potentially positive effects, with a small extent of evidence."
Discussion¶
Related Claims¶
- The WWC rated DreamBox Learning as having potentially positive effects on mathematics achievement with a small extent of evidence — related
- Spelling Mastery produced statistically significant positive effects on all three writing measures in a fourth-grade RCT against Visual Imagery instruction — a narrower finding that bears on this claim
- Spelling Mastery showed substantively important but not statistically significant positive effects on all four writing measures in a grades 2–4 RCT against basal spelling instruction — a narrower finding that bears on this claim
- On the TWS-3 subtests in the 2006 RCT, Spelling Mastery favored the Predictable Words subtest (effect size 0.57, WWC-adjusted p = 0.07) over the Unpredictable Words subtest (effect size 0.11) — a narrower finding that bears on this claim
- WWC rates MTP-S as having potentially positive effects on general achievement, with a small extent of evidence — related
Page metadata
| Field | Value |
|---|---|
type |
claim |
id |
spelling-mastery-potentially-positive-writing-ld |
title |
Spelling Mastery has potentially positive effects on writing for students with learning disabilities, based on two RCTs with a small extent of evidence |
description |
Spelling Mastery has potentially positive effects on writing for students with learning disabilities, based on two RCTs with a small extent of evidence |
status |
review |
evidence_strength |
moderate |
newest_evidence |
2014 |
source_checked |
2026-10-20 |
generated |
by process:wiki-ingest on 2026-10-07 |
trust |
unverified — no one has confirmed this page's content |
sources |
1 — wwc-summary-1 |
Frontmatter is the page's machine-readable record — see the Schema & Guide.