Background Morphological analysis skill is the ability to problem‐solve meanings of unfamiliar words by applying knowledge of morphological constituents. For vocabulary words from the academic layer of English, the major, meaning‐carrying morphological contituents are Latin roots (nov meaning ‘new’ in innovative). The degree to which morphological analysis skill using Latin roots is susceptible to intervention and whether improvements relate to reading comprehension remains unclear. Methods We investigated the effects of a morphology intervention designed to promote academic vocabulary learning, morphological analysis and reading comprehension with 140 adolescent, multilingual learners in US schools (intervention n = 70; comparison n = 70). We estimated direct effects of the intervention on morphological analysis and academic vocabulary knowledge and examined whether they mediate intervention effects on reading comprehension. Academic vocabulary was measured as both definitional and multidimensional knowledge. Results We found significant, direct effects of the intervention on morphological analysis skill and academic vocabulary knowledge. Additionally, we found a significant indirect effect on reading comprehension via academic vocabulary and a marginally significant indirect effect via morphological analysis skill. Notably, the indirect effect of academic vocabulary was evident only for multidimensional, not definitional knowledge. Conclusions Findings extend current understanding about how morphology intervention promotes vocabulary and reading comprehension improvement for multilingual learners. (word count = 207)

Since well before the release of the National Reading Panel report in 2000, phonemic awareness has been an important topic for reading researchers. However, it is unclear the extent to which commercial materials for phonemic awareness instruction are consistent with that report and subsequent research. In the current study, we investigated the use of commercial kindergarten materials for such instruction in one state and suggest that the most widely used materials have areas of inconsistency with the science of reading. Notably, the commercial materials reviewed here did not take orthographic development into sufficient account. Additionally, the materials did not use letters and did not limit focus to one or two skills. Implications for classroom instruction, teacher education, commercial materials development, and future research are identified.