Effective vocabulary interventions for young emergent bilinguals: A best-evidence synthesis

This best-evidence synthesis appraises the design and outcome characteristics of vocabulary intervention studies conducted with preschool through 6th grade emergent bilingual (EB) children and spotlights rigorously designed studies for which effects could be better attributed to instructional features. Twenty-nine selected studies were analysed for the design characteristics of attrition, random assignment, and baseline equivalence as well as the outcome characteristics of reliability and outcome alignment. Following suggestions from the What Works Clearinghouse (2020) guidelines, levels of evidence for effectiveness were determined for each treatment-comparison group contrast. Studies meeting effectiveness standards were further analysed to determine intervention impacts (i.e., effect size) on EBs' English word learning. Analyses revealed that 17 studies (59% of the sample) were experimental and employed random assignment whereas baseline equivalence was established for most of the 12 quasi-experimental studies (41% of the sample). Attrition did not plague the majority of vocabulary intervention studies. The outcome measures of all but one study showed satisfactory reliability indices, 85% of which showed alignment across treatment and comparison groups. Thirty-six measures (65% of measures) across 21 reviewed studies (72% of studies) met acceptable levels of evidence of effectiveness. Most studies employed standardised vocabulary measures to assess EBs' growth in breadth rather than depth of vocabulary knowledge. The significance of outcome measures with large, medium and small posttest effect sizes are discussed relative to their oral/written, receptive/expressive, definitional/contextual and depth/breadth vocabulary characteristics. Implications address significant knowledge gaps regarding EBs' English vocabulary intervention and highlight issues and recommendations.