The students’ heterogeneity in this study was unpacked through two
dimensions: the nationality of the students and their achievement or ability.
In each of the 4 studied classes, 5 separate learning groups with 5 students
in each were formed. Within the first three classrooms, three different
types of groups were formed. The groups were either homogeneous (all
high achievers or low to intermediate achievers), and heterogeneous mixed
(two high achievers and three low to intermediate achievers). Students
were not randomly assigned to either of the groups but considering a fair
distribution of the available nationalities all over the groups unless the
group is set to be entirely homogeneous (i.e. through both the nationality
and ability dimensions). Each student was then given a personal
identification code number.
Table 2 shows the composition and the distribution of the students among
the studied classes. Three of the studied classes contained mixed ability
students from different nationalities who formed entirely heterogeneous
groups. Each group contained at least three different nationalities, one high
achiever, two intermediate achievers and one low achiever (at risk student)
unless stated otherwise. However, the fourth class contained only high
achievement students from different nationalities. The groups formed in
that class were heterogeneous only by the nationality dimension. Table 3
shows the numbers and the distribution of the students over the studied
groups.