Kindergarten, along with the child's family, is the main initiator of the child's development and because of that, continuous improvement is necessary for good success in it. For many years, the question of how to enable this and what to change in the system has been important, so, apart from the organization of groups according to the same chronological age of children, which has existed for many years, a new method appears, age-heterogeneous kindergarten groups. The innovative way of grouping led to the opening of new questions and even more polemics, both between educators and other professional associates, about what is the best long-term and correct decision for children and what will really enable them to develop in the best possible way. While homogenous groups are formations attended by children of the same chronological age, which are established and unconditionally accepted in many preschool institutions, heterogeneous, or in other words, mixed-age groups are those that contain children of different ages and are often underestimated, considered as something complicated, exhausting, even burdensome. Although many research proves that both approaches to organizing have both desirable and undesirable factors, after a long time of representation of homogeneous groups, heterogeneous ones still prove to be a better choice in many fields. They include a larger range of abilities, competences and skills that are positively influenced equally by younger and older children, and is mostly reflected in social and emotional competences. Furthermore, play, which is the most important segment of a child's life, in heterogeneous groups also contains additional benefits that are different than in a homogeneous group.