Systematic review and meta-analysis of the implementation and effectiveness of spelling instruction and intervention

It is important for students to develop spelling skills, and spelling skills have been found to benefit the development of reading and writing skills. Past reviews and meta-analyses supported the effectiveness of spelling instruction at improving a variety of academic outcomes including spelling, reading, and writing. This review and meta-analysis contributes to this research and extends the current research on the impact of implementation characteristics on effectiveness. This review and meta-analysis included 81 studies (43 group design and 38 single-case design [SCD]). The meta-analysis indicated an average effect of spelling instruction and intervention that was small in the group design research (g = 0.319) and moderate in the SCD research (Tau-U = 0.578). Implementation and methodological characteristics were described, and the nature of the comparison conditions and dependent variable were identified as potential moderators. A significant sample of research represented a range of participant samples, implementation characteristics, instructional practices, and methodological attributes. These results suggest that experimental spelling approaches are generally a modest improvement on existing approaches and that little research has investigated the effectiveness of some best practices, including practices that support individualization of spelling instruction. The included studies found overall small to moderate positive effects of spelling instruction and intervention on student spelling performance. Spelling instruction and intervention approaches investigated in the research are likely to be significantly better than providing no instruction, but modestly better than another instructional approach. Existing spelling instruction and intervention approaches are most likely to improve performance on taught words but less likely to improve performance on words not taught.