The objective of this review is to assess the effectiveness of interventions aimed at students with or at-risk of academic difficulties in grades 7 to 12 for increasing academic abilities and enhancing educational outcomes, as measured by standardised tests in reading and mathematics. The analysis will centre on the comparative effectiveness of different types of interventions in an attempt to identify those intervention components that have the largest and most reliable effects on academic outcomes as measured by standardised test scores. In addition, evidence of differential effects for students with different characteristics will be explored, e.g., in relation to age or grade, gender, and socioeconomic status. The review will also examine moderators related to study design, measurement of effect sizes, and the dosage and delivery of interventions. The review aims to provide policy makers and educational decision-makers at all levels -- from governments to teachers -- with evidence of the effectiveness of interventions aimed to improve the results of students with or at-risk of academic difficulties.