This document presents a review of evidence commissioned by the Education Endowment Foundation to inform the guidance document "Improving Mathematics in Key Stages Two and Three" (Education Endowment Foundation, 2017). The review draws on a substantial parallel study by the same research team, funded by the Nuffield Foundation, which focuses on the problems faced by low attaining Key Stage three students in developing their maths understanding, and the effectiveness of teaching approaches in overcoming these difficulties. This project, "Low attainment in mathematics: An investigation focusing on Year 9 pupils" includes a systematic review of the evidence relating to teaching of low-attaining secondary students, which the current report builds upon in the wider context of teaching maths in Key Stages two and three. The purpose of the review is to synthesise the best available international evidence regarding teaching mathematics to children between the ages of 9 and 14 and to address the question: what is the evidence regarding the effectiveness of different strategies for teaching mathematics? Additionally, a set of more detailed topics developed by a group of teachers and related to aspects of pupil learning, pedagogy, the use of resources, the teaching of specific mathematical content, and pupil attitudes and motivation are addressed. Using these topics, the authors derived the 24 research questions that they address in this review. Using a systematic literature search strategy, 66 relevant meta-analyses were identified, which synthesise the findings of more than 3000 original studies. This review begins with an executive summary with the study's headline findings. Then, the authors' theoretical understanding of how children learn and develop mathematically is provided in Section 3: The development of mathematics competency. In this section, they summarise a range of background literature that they used to inform their analysis and synthesis of literature. Sections 4 and 5 provide a guide for the reader and describe the method used in the study. In the subsequent sections, findings are presented relating to the 24 detailed questions. [For the related guidance report, see ED612294.]