In recent years, reflection on pedagogical tact has made a comeback in the international debate. Tact is a fundamental disposition of the educator, albeit one that is scarcely addressed in the training of teachers and educators. The question is whether it is possible to treat this pedagogical propensity as a teachable habit, and to what extent. Here we propose that tact can be understood as a teachable frame of mind of the educator by analysing tactlessness. In other words, in order to become a tactful teacher, one has to pass through situations in which tact is not enacted, because the absence of tact -- as Adorno proposes in his dialectical-negative perspective -- becomes a condition for soliciting doubts about one's educational action, metareflexive rethinking and finally tactful responses.