A majority of the challenging words that adolescent readers encounter in school texts are morphologically complex and from the Latinate layer of English. For these words, bound roots carry important meaning, such as the relation between innovative and its bound root, nov, meaning "new." This study investigated the effects of instruction about bound Latin roots on academic word learning and morphological problem-solving skill with English Learners (EL) at three grade bands: Grades 6-8, 9-10, and 11-12. Employing a within-subjects design, 82 students participated in two counterbalanced intervention conditions: an academic vocabulary without morphology (comparison condition) and a morphology-focused academic vocabulary intervention (treatment condition). The largest treatment effects were observed for oldest students, but positive effects were observed at all grade levels. Results suggest that instruction focused on the major meaning-carrying components of academic words of the Latinate layer in English--bound roots--is especially effective for ELs in the secondary grades. [This paper was published in "Reading Psychology" v38 n3 p262-288 2017 (EJ1126574).]