Education is said to be the major engine of a nation`s sustainable future that envisages achieving a living standard that meets the needs of the people, mainly by providing the route for scientific and technologic progress, culture vitality and social cohesion. Indeed, through time, it has been highly discussed issues regarding student success and achievement. In this context, we may ask ourselves which one works the best for obtaining more favorable educational outcomes – ability grouping or mixed learning, that is, homogeneous or heterogeneous classrooms?
Heterogeneous grouping has intrinsic two main ideas. The first refers to the situation whereby students with different intellectual ability learn together in the same classroom, while the second indicates within-classroom groupings in which “students of varying abilities learn together in cooperative learning arrangements”. On the contrary, ability grouping can be regarded as a practice that distributes students among classrooms taking into account their perceived capacities for learning, thus students of similar academic level are placed within the same group for instruction. In particular, although the Portuguese law demands that residence should be the criteria of allocating students to different schools, my perception is that public schools tend to pick students according to their socioeconomic background and academic performance with the main goal being achieving a higher reputation in the market. In fact, I believe that these selection mechanisms are nowadays politically and socially accepted that sometimes is even instigated by some experts in the field.
Relatively to the main advantages associated with heterogeneous grouping, its proponents have argued in favor of skill building and improved reading levels thanks to teamwork practices as students try to regulate mutually. They typically point out as an example the Collaborative Strategic Reading, whereby students are able to share and teach each other. On the other hand, ability grouping is defended as a practice that stimulates academic achievement by allowing teachers to focus instruction on like-ability students thus “adjusting the pace of instruction to students´ needs”. In the Harvard Education Letter, Leon Lynn and Anne Wheelock state that “schools that reserve the highest quality educational opportunities for the “best” students -as determined by a selection process that is often flawed and discriminatory – are denying many students the opportunity to achieve their full potential”. Emily et al (2003) found out that grouping by ability deprives low-ability students of opportunities to learn effectively and peer, personal and teachers´ expectations of poor performance may end up reducing their motivation. Nevertheless, Lou et al (1996) showed that assigning high-ability students to a heterogeneous class may create inappropriate incentives as they will spend time helping their peers instead of learning something new. An interesting work by Melser (1999) “measured the self-esteem of gifted students in homogeneous groups and compared them” to the ones in a heterogeneous class. The result indicates that gifted students in the heterogeneous group have a boost in their self-esteem, while when included in a homogeneous setting their self-esteem decreases. In the US, McEwin, Dickinson, and Jenkins (2003) concluded that 78% of middle schools in 2001 used some degree of ability grouping. Hence, this result emphasizes the trend to move towards homogeneous classrooms as recent studies showed that the academically strongest benefit more from ability-grouping, especially in subjects as science and maths.
Finally, how much differentiation is it too much? If girls, who are said to be more collaborative in the classroom and boys, who tend to be more competitive in class differ significantly, does that mean that schools should incentivize single-gender schooling?
 Effect of homogenous and heterogeneous ability grouping class teaching on student’s interest, attitude and achievement in integrated science, Adodo S. O.* and Agbayewa J. O, Science and Technical Education Department, Adekunle Ajasin University, Akungba Akoko, Ondo State, Nigeria, 18 January, 2011
 A widely publicized 1992 study by the American Association of University Women reported that girls appear to benefit greatly from single-gender classrooms