The aim of this review was to support the Education Endowment Foundation (EEF), other funders, and developers and deliverers scaling-up interventions by undertaking, for the seven effectiveness trials that had been completed by 2019: (1) a quantitative comparison of effect sizes at the efficiency and effectiveness stages; and (2) a qualitative analysis of interviews with developers and deliverers who have been engaged in scale-up from an EEF efficacy trial to an effectiveness trial, to identify any models, supporting structures, and programme features that either support or hinder intervention scale-up to large numbers of schools. The findings indicate that the there is scope for a more systematic and evidence-based approach to supporting developers to scale-up their interventions that includes greater clarity around what is necessary to reduce or change to implement at scale, builds on evidence on effective approaches to training trainers and CPD for direct implementers, and highlights the need for robust quality assurance of training and implementation. Funders may also wish to consider in more depth how an 'effectiveness trial' should be defined, including whether it is appropriate to change the target group. [For "Review of EEF Projects. Evaluation Report," see ED625480. For "Review: EEF Implementation and Process Evaluation (IPE) Quality Pilot," see ED625478.]