“…First of all, deep-level collaboration inevitably requires touching teachers' underlying beliefs, which will inevitably lead to disagreement and conflict. This seems difficult because teachers tend to restrict collaboration to more safe and less threatening aspects, focusing on psychological safety and cohesion, avoiding conflict, and preserving their norms of privacy and autonomy (Achinstein, 2002;Gajda & Koliba, 2008;Gunn & King, 2003;Hargreaves, 2001;Levine & Marcus, 2010;Lima, 2001;Ohlsson, 2013;Somech, 2008;Supovitz, 2002). Striving for an optimal balance between room for cognitive conflict and constructive controversy on the one hand and a focus on personal ties on the other hand proved to be a challenge in teacher collaboration (Kelchtermans, 2006;Lima, 2001).…”