The necessity to collaborate has become increasingly strong in schools across several countries (Lessard, 2005, Gather-Thurler, Maulini, 2007, Marcel et al., 2007, Tardif and Borges, 2009, Portelance, Borges, Pharand, 2011). Relating to a new teaching professionnality, teaching collaborations could be described as the transition from an individual to a collective practice (Marcel et al, 2007). This type of collaboration encompasses the collective responsibility by teachers, in relation to students' academic success by linking it to school projects and the cohesion of school.

In France, the last 2013 law for the re-founding of French Schools laid "the foundations of a fair, demanding and inclusive school". This included the conditions to increase all student results and to reduce the impact of social determinism. Priority was given to primary schools. This is the period during school when basic learning commences and when school failure can be prevented.

Within the frame of this law "more teachers than classrooms" (Plus de maîtres que de classes, PMQC) measure is introduced at the beginning of the 2013 school year, in schools receiving a high level of pupils with learning difficulties.

This implementation of a supernumery teacher (ST) must lead school teachers to change both their teaching and their collaborative practices.

The objective of this publication is to highlight the various internal teacher partnerships with the same non-coercive institutional measure. This contribution focuses on the new ST role introduced by this measure in French schools. It seeks to answer the following questions: Which types of collaboration emerge with the assignment of a ST in the school? What are the professional dynamics of these STs who are no longer responsible for a class of students? To what extent can they benefit from professional development in work situations?

The theoretical framework develops three major notions:

The first concerns work-sharing between teachers (Piot & Marcel, 2009), both inside and outside the classroom. The ST’s presence in the school strongly encourages work-sharing. Usually teaching collaborations were primarily made by affinity (Barrère, 2002) between two or more teachers. Teacher work-sharing is part of an emerging professional space, between the class levels and that of the school. "Work-sharing is not a mode of "extra" teaching work that would be added to teacher’s  traditional work, alone in his classroom" (Piot and Marcel, 2009, 8). It involves professional activities carried out by teachers that are implemented in schools (Marcel and Garcia, 2009). Three types of work-sharing can be distinguished according to an increasing degree of intensity: coordination, collaboration and cooperation (Marcel, Dupriez & Périsset Bagnoud, 2007).

The second part concerns the notions of partnership. It has two radically different meanings. One can refer to the division and distribution of a task, whereas the other one is about the connection when it comes to sharing responsibility with someone or playing more active roles in the same project (Pelletier, 1997, Merini, 1999). The nature of the partnership varies. Landry's (1994) distinction of three relational modes - service partnership, associative partnership and reciprocal partnership - will serve as partnership gradients.

Finally, the last section develops the co-teaching notions which constitute new organizational forms in the implementation of these measures. We will expose the Friend & Cook (2003) typology, the most often used, which presents six organizational configurations.

The data analyzed in this article stems from an ethnographic inquiry carried out during two school years 2013-2014 and 2014-2015 in which the researcher took position as a neutral observer and comparator posture (Hughes, 1996). This comparative ethnographic survey on PMQC implementation measures, had been carried out in three primary schools located in the same West of France academy. We selected three same sized schools and 6 to 7 classes for three reasons. First of all, in each of them, a ST was assigned full-time to the school. Further, the ST's teaching takes place in all classrooms because teachers consider that the PMQC should benefit all students in the school. Finally, these schools have contrasting PMQC organizations. Teacher work-sharing was studied from a researcher's immersion program during a several day period in each school over the two school years. In this paper, we focus on interindividual work-sharing between teachers responsible for a pupil's group (TR) and the ST from the ST's point of view. To do this, the weekly ST schedules in each school were collected with the ST's explanations. In order to understand the interindividual reasoning, we interviewed the ST. For each one, two comprehensive semi-directive individual interviews (Kaufmann, 1996) are held at the end of the school year. The data processing mode is a qualitative analysis (Miles & Huberman, 2003). Firstly, in a descriptive approach, the analysis of the schedules resulted in a categorization of the organizational arrangements between the RT and the ST in each school over these two years. Then a comparison was made between the three schools. Secondly, in a comprehensive approach, we have to proceed to a sequenced thematic analysis (Paillé & Mucchielli, 2013) of the interviews. We sought to reveal the terms of negotiation (Mérini, 1999) operated between the RT and the ST as well as the STs' dynamics and professional development in various work situations.

The first results show the level intensity of their collaborations (Marcel et al., 2007). The first one corresponds to work-sharing when the ST-RT negotiation is established in relation to the importance of the difficulties reported by the RT with their pupils. Then, it is the coordination of the ST's teaching direction towards this or when the RT needs help. This organization refers to the pedagogical scenario negotiations between the RT-ST dyads. A second level relates to their collaborations. Here we can note that, the ST teachings are negotiated on the same level as a teachers' group who are responsible for the same class levels. This collaboration seems to be built by a teachers' association under the ST 's impetus. Based on a common learning project, teachers agree to adjust teaching assignments and share these amongst them for pupils coming from one or several classrooms. Finally, the last intensity level shows their cooperation. The school teachers decide together on the ST's pedagogical teachings and means of action. After their lessons, they talk about their pedagogical and didactic effectiveness in the classrooms. The negotiating criteria used to decide on the ST's teaching practices shows the added value brought to the school project. In this organization, disagreement discussions are an integral part of their mind sets in the teaching and their professional development. These three modes of work-sharing highlight various ways of managing student diversity and difficulties. They also show several ST's inclusion / exclusion classroom modes. Three types of professional dynamics emerge among ST’s in particular as regards to school-based ‘Continuing Professional Development’ and their professional directions. This is what we will deal with in depth during the communication conference.

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