One of the major factors in helping effective teaching is differentiated instruction. What is the differentiation instruction? The National Curriculum Council defined it as "the process by which curriculum objectives, teaching methods, assessment methods, resources and learning activities are planned to cater for the needs of individual pupils". Differentiated lesson beyond the pupils' learning that take place gives many advantages. Teachers who differentiated their lesson in the mixed ability classroom find that it will lead to increased students' achievement and offer quality education. In their investigation, Stavroula, Leonidas and Mary (2011) showed that differentiation promotes all students to improve their achievement. The study was concerning the application of differentiated instruction in mixed ability classes, in which Cypriot pupils participated and provides evidence about the effect that differentiated instruction in mixed ability classes has on students' achievement. The results of the experimental group that had received differentiated instruction were compared with the results of the control group that had not received differentiated instruction. Final results from this research shown that regardless of the students' ethnic group, group of pupils that had received differentiated instruction had scored highest in test compared to the group that had not received differentiated instruction. Therefore, implementation of differentiated instruction can enhance the learning process and improve students' achievement. Differentiation is not the way out of ineffectiveness, but it can contributes to achieving effectiveness for all students. This work is reinforced by a study by the Oshawa Central Collegiate Institute (2009) who investigated the impact using differentiated instructional approaches in the classroom would have on students' achievement. This study was carried out with the help of some teachers of various subjects.