The paper begins with a discussion of the strategy of the Institute of Education of the Republic of Slovenia, which focuses on branch schools and in particular on multiclasses departments.

The situation in Slovenian schools with regard to multiclass teaching is described. The Slovenian primary school curriculum prescribes the achievement of a uniform (at least minimum) standard of knowledge, independently of the organisational, staffing, ethnic, financial and environmental diversity of schools or departments. The following presentation of the Slovenian education system is intended to draw attention to the number (percentage) of schools that teach in muliclasses departments. Such departments include pupils from two, three or even four different grade combinations or two, three or four age groups of pupils, which poses a great challenge for teachers in terms of organising and delivering lessons.

In this paper we present an analysis of teachers' responses to the question about the organisation and delivery of lessons. We are talking about lessons in which one teacher works with one age group of pupils in the same room at the same time, while the others work quietly and individually.

This type of organisation has its advantages for pupils in developing independent learning. However, it is less likely that pupils in such departments will develop 21st century skills, abilities, competencies and literacies in an intensive way. Therefore, in our development work with teachers in multiages departments, we try to develop the most appropriate didactic strategies where active learning is present as much as possible among the pupils to develop 21st century skills and competences.

A leading didactic strategy based on social constructivism, which plays a key role in guiding the work of multiclasses groups, is the so-called formative monitoring. In such circumstances, it is imperative for educators to implement suitable didactic strategies in the classroom that foster teamwork and the development of transversal skills such as critical thinking, collaboration and self-regulation. Teaching staff, particularly those in multiclasses departments, are presented with significant opportunities to cultivate these competencies. There are many opportunities for intergenerational cooperation and learning from each other, which is less pronounced in larger, homogeneous departments. This pedagogical approach is founded on the principles of interdisciplinarity, aligns with the specific principles of mixed ability groups and emphasises the involvement of the school in the local environment, where pupils solve authentic challenges.

Keywords: Multiages learning groups, interdisciplinary learning approach, learning strategies, intergenerational learning, transversal skills development, branch schools.