This literature review focuses on achieving educational equity through catering for differences in students' instructional needs. In heterogeneous classes the need for tailored direct teacher instruction is dependent upon students' instructional needs. Realist review methodology is used to study how instructional strategies can add to catering for students' different needs. The focus lies on two proactive strategies in which teachers cater for these differences, namely preteaching and extended instruction. The aim of this realist review is to verify how preteaching and extended instruction may contribute to catering for students' different instructional needs. It is noticed that the complexity of differentiated teaching is not always reflected in studies on preteaching and extended instruction. The focus of many studies lies in measuring learning progress in a linear and fixed way for a selected group of students which is not aligned with theory on differentiated instruction which suggests cyclical teaching processes. To respond to students' needs ongoing monitoring of cognitive and affective indicators of learning is needed. Implications for theory and practice are discussed.