Professional Learning Communities (PLC's) is a vibrant topic and PLC’s are considered highly relevant for the professional development of schoolleaders (and teachers). Since I worked in the early eighties with the International Network of Principals’ Centers (at that time at Harvard) I also was convinced of that.
The INPC (Roland Barth) was built on the conviction that then-current (academic) training for schoolleaders was not very useful. Instead principals themselves should organise their own inservice training, meeting in self-chosen groups on self-chosen topics. And the main instrument during the meetings was ‘conversation' that we now would qualify as ‘deep conversation’. (See e.g. Tamara Homund Nelson e.a. *1). INPC was a success for almost three decades. *2
In the nineties and beyond professional development for schoolleaders in many countries became increasingly and thoroughly designed and organised at national and sub-national level, at times with considerable or even large budgets. Profiles for schoolleaders were designed and detailed as well as requirements for training, and by preference evidence-based. There seemed to be no place anymore for initiatives by principals themselves till recently.