In most schools today the primary consideration for homogeneous grouping is based on

Grouping in the classroom: In our schools, the students are organized in grades or classes based on their level of achievement in the prescribed curriculum. Grouping help and guides students in the formation of the right types of groups to achieve the desired results. The students placed in a class, by and large, belong to the same age group.

Grouping based on Ability:  Grouping based on ability levels alone is attempted if the primary learning goal is the enhancement of students' attainments. In the context of ability levels, the groups can be homogeneous and heterogeneous. 

• Homogenous Group: In these groups, all members of the group are of the same ability or attainment level: high, average, or low. 
  • Homogeneous or ability grouping refers to the process of teaching students in groups that are stratified by achievement, skill, or ability levels.
  • It provides opportunities for students to learn at their own pace and ability.
  • This type of grouping is frequently used in classrooms and schools to increase reading achievement. 
  • Homogeneous groups of students can progress and move from one ability level to the next when the focus is set on their ability of concern. 
• Heterogeneous Group: Heterogeneous group students of different ability levels are included. 

NOTE: 

• Grouping based on Age level and Grade level is not much need for the attainment of learning goals. 

From the above, we can conclude that In most schools today the primary consideration for homogeneous grouping is based on ability level.