The size of group for collaborative and cooperative learning should be as small as possible as it provide scope for independent participation where as in large group few students have the scope of not to participate in the group.
5 is the ideal number of students for collaborative learning.
In a research study of collaborative groups some years ago, we used the term collaborative small groups as we were researching groups of about four learners; see:
Chapter Co-Learning in the Collaborative Mathematics Classroom
Los aprendizajes, tanto colaborativos como cooperativos, deben ser realizados por grupos no mas de 6 alumnos los que serán elegidos por los profesores y antes de empezar con la clase, los alumnos deben elegir a un líder , el que comandará a su grupo , produciendo al final una discusión entre todos los grupos