In Australia, a substantial proportion of students start secondary school with literacy and numeracy skills that are 3 or more years below those of their peers. Evidence suggests that low literacy and numeracy skills hinder students' access to the curriculum and can result in poor progress or educational failure. These students are also more likely to face poor outcomes post-school, such as in their health and employment. A large body of research has been conducted on literacy and numeracy instruction and interventions for primary school-aged students, as fundamental skills in these domains are generally taught as part of the primary school curriculum. However, less is known about the applicability or effectiveness of interventions for older students who have not mastered these foundational literacy or numeracy skills. Questions also remain about the feasibility of implementing literacy and numeracy interventions within secondary schools, where teachers are typically less familiar with teaching these basic skills and where scheduling constraints exist. In this report, the authors present the findings of an umbrella review to address these gaps in knowledge. [This report was produced with Monash University.]