This report presents findings from exploratory, descriptive meta-analyses of effect sizes reported by the first 82 EEF evaluations that used a randomised controlled trial (RCT) or clustered RCT impact evaluation design published up to January 2019. The review used a theoretical framework derived from literature with five overarching themes to group explanatory variables: (1) Intervention; (2) Implementation & fidelity; (3) Theory & evidence; (4) Context; and (5) Evaluation design. Meta-analyses of effect sizes reported for intention-to-treat (ITT) analyses of primary attainment outcomes, ITT analyses of secondary attainment outcomes and free school meals (FSM) subsample analyses of primary or secondary attainment outcomes are reported. Effect sizes reported for psychological outcomes were also examined but not included in the meta-analyses because of the distinct and diverse nature of these outcomes. Also presented are findings from trial/evaluation-level descriptive analyses of cost effectiveness of interventions and overall pupil-level attrition. [For "Review of EEF Projects. Summary of Key Findings," see ED625481. For "Review of EEF Projects. Technical Annex," see ED625484. For "Review: Scale-Up of EEF Efficacy Trials to Effectiveness Trials," see ED625479. For "Review: EEF Implementation and Process Evaluation (IPE) Quality Pilot," see ED625478.]