Understanding the major societal problems of today and tomorrow in the school context poses formidable didactic challenges. Their study assumes that students acquire the means to decipher the complex interactions that characterize them by linking a large number of factors from both the natural sciences and the human and social sciences, while raising political and ethical issues that are explicitly or implicitly referred to value systems (Audigier, Fink, Freudiger & Haeberli, 2011 ; Audigier, Sgard & Tutiaux-Guillon, 2015). This is particularly the case for themes such as energy, climate change, mobility, supply and migration, which can all be referred to in the Anthropocene - an era of risk.

To this end, it is essential that the school allows students to build operational thinking tools to organize perceptions and knowledge by networking them. Such thinking tools - integrative concepts of disciplines, tools of the systemic, ability to problematize, etc. - are the ones that students need to appropriate to be able to understand and think about complexity. If we refer, for example, to the definition of complex thinking proposed by Edgar Morin (1990/2015), implementing complex thinking presupposes the ability to identify and mobilize causal links in a reasoning (not only linear causality, but also relationships with multiple causes or effects, as well as syllogisms), feedback or recursion loops, situations of dialogic tension, relationships based on the hologramic principle (the part is in the whole, and the whole is written in the part). We add the ability to identify and mobilize relationships through which one or more disciplinary ways of thinking are expressed, for example those of geography, history or biology (Jenni, Varcher & Hertig, 2013; Hertig, 2015, 2017). Without relying on the same theoretical foundations, other research leads to the proposal of models whose spirit is ultimately very similar (see e. g. Mehren, Rempfler, Buchholz, Hartig & Ulrich-Riedhammer, 2017).

What learning situations should students be offered to develop the intellectual tools they need to think about complexity, and how can they be made aware of it (metacognitive focus)? One of the first didactic challenges is to get students to understand that the spontaneous mode of reasoning that reduces any explanation to monocausality or a chain of linear causalities is powerless to give intelligibility keys of the world - even though this type of reasoning is omnipresent in common sense speeches and frequent in the media (or even in school textbooks!). Another central issue is that the proposed teaching units lead students from primary school onwards to appropriate tools that enable them to identify the constituent elements of a system and the types of links between these elements, for example by using graphical representation to report on their analysis (Assaraf & Orion, 2005; Bollmann-Zuberbühler & Kunz, 2008; Rempfler & Uphues, 2012). A third fundamental challenge lies in learning problematization: developing the capacity to problematize is a necessity for students to build their autonomy and ultimately their ability to mobilize critical thinking. These various challenges will be recognized as essential components of an education for sustainable development conceived as an education with an emancipatory purpose. Finally, it is important not to overlook a key issue at another level, namely the initial and in-service training of teachers, who are often uncomfortable in proposing learning situations that effectively enable students to build their ability to think about complexity.

After a brief summary of the context of the research and the methodology used, the presentation will focus on the results of the analyses carried out on the first data collected in classes and from primary and secondary school teachers.

The research is conducted in French-speaking Switzerland by a multidisciplinary and inter-institutional team under the aegis of the LirEDD (International Research Lab on Education for Sustainable Development). The academic year 2017-2018 was devoted to the preparation of the project and the authorisation procedures for data collection - procedures that are unfortunately long and (unnecessarily) complicated and differ from one canton to another, due to federalism. Data collection began during the 2018-2019 academic year and will continue until 2020-2021. The research objectives are expressed through five research questions: 1) What thinking tools do partner teachers identify and implement in their teaching to enable their students to understand complex social objects or situations? 2) To what extent do students grasp these tools and are they able to implement “complex thinking”? 3) Do learning about problematization and the practice of scientific investigation approaches promote the development of "complex thinking"? 4) What are the contributions of graphic visualization approaches (mapping, modelling, conceptual maps, mental maps,...) for students and partner teachers to understand complex objects or social situations? 5) What are the contributions of a collaborative research design to the development of teachers' professional skills? This collaborative research will lead to the collection of various types of data: semi-directive ante and post interviews with partner teachers, student productions (written traces, posters, etc.), teachers' productions (lesson plans, course materials, various artifacts), video recordings of selected moments of the teaching units (problematization phase, moments in which "complexity is present", synthesis phase), as well as semi-directive interviews with groups of students (focus groups) that will take place a few weeks after the end of the classroom teaching sequence. Interviews with partner teachers and student groups will be conducted using audio recordings. In addition, the collaborative research design is based on an interdisciplinary discursive community of practices, which also allows data collection during times when partners (researchers and teachers) work together (video recordings, written traces, artifacts). Data recorded in audio or video will be transcribed. The ambition of the research team is to work each year with about ten to twelve partner teachers and their classes, in primary and secondary levels of compulsory schooling, as well as in post-compulsory levels (high schools and vocational schools). Most of the data collected will be analyzed using qualitative methods, including conceptualizing category grids (Paillé & Mucchielli, 2003). The transcribed data corpus may also be processed using text analysis software.

The analysis of the data from a first research project devoted to a similar theme and conducted between 2012 and 2016 showed in particular that a significant proportion of pupils in Secondary 1 level (12 to 15 years old) mobilize elements of complex thinking, in particular linear causal relationships between two or more elements, more rarely multiple chains of causality. In the interviews, students are also able to mobilize various spatial and temporal scales, feedback loops or dialogical tensions. On the other hand, with regard to the identification of actors involved in a complex social situation, students' comments show a predominance of undifferentiated actors ("people", "one", "they"). The passage to action and the conditions of action are also largely absent from students' discourse (Pache, Hertig & Curnier, 2016). As for partner teachers, they tend to confuse "complex" and "complicated" and generally reduce complexity to multiple, so that there is a dilution of disciplinary knowledge in cross-cutting research, comparison and information organization procedures, to the detriment of an explicit identification of complexity thinking tools. The contributions of the current research should help to refine and nuance the results of previous research. For example, the use of the interdisciplinary matrix, an a priori analysis tool for teachers (Gremaud & Roy, 2017), should enable them to enrich the problematization phase of their teaching units. More broadly, the results of the research can be integrated into initial and in-service teacher training and teacher guides accompanying textbooks. This should in the long term encourage an evolution of teaching practices giving an increasingly consistent place to investigative approaches that really allow students to build their ability to think about complexity. In the shorter term, the collaborative research design should have the same effect on the scale of partner teachers' practices.

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