A major problem for teachers is that students are different, they learn mathematics differently, and at different rates. Regardless of this, schools organise students into large groups or classes of 20 to 30 students all about the same age. Then there is the "Australian Curriculum: Mathematics" that states the student learning outcomes that are expected for students at each Year level of school -- which means at each year of their lives. Teachers are expected to teach the curriculum prescribed for students of the specific age group in their class and still keep in consideration student differences. How does a teacher of primary mathematics deal with the range of student thinking and knowledge in his or her class every day? Teachers face many challenges when catering for the diversity in their classrooms. One way that schools sometimes try to overcome these challenges is by grouping students according to ability. This article discusses if this is a solution to the problem.