Low levels of mathematics and reading skills are associated with a range of negative outcomes in life, including reduced employment and earnings, and poor health. This review examines the impact of a broad range of school-based interventions that specifically target students with or at risk of academic difficulties in Grades K-6. The students in this review either have academic difficulties or are at risk of such difficulties because of their background. Examples of interventions that are included in this review are peer-assisted instruction, using financial and non-financial incentives, instruction by adults to small or medium-sized groups of students, monitoring progress, using computer-assisted instruction, and providing coaching to teachers. Some interventions target specific domains in reading and mathematics such as reading comprehension, fluency, number sense, and operations, while others also focus on building different skills, for example, meta-cognition and social-emotional learning. The review looks at whether these interventions are effective in improving students' performance on standardised tests of reading and/or mathematics.