The purpose of this book is to provide an evidence-based theoretical practical model for professional development of pedagogical specialists in Bulgaria, Romania and Serbia. The framework steps on two key strands of knowledge, linked to online teaching evaluation and mentoring provision, informed by Jim Knight's impact cycle model. The model is tested through a transnational piloting exercise, involving 64 teachers from the three targeted countries. Despite the short duration of mentoring activities, participating teachers confirmed the added value from this intervention on various dimensions such as: increased professional self-confidence and motivation for development and improved students' engagement. The collected evidence confirms the opportunity for national policy-makers to reconsider the overall strategic approach towards teachers' professional development pathways and place further emphasis on internal support measures such as peer mentoring. [The publication is created within the European project "ProTeach," which includes three organizations: the Bulgarian Union of Teachers (SEB), Teachers Union of Serbia (TUS), and the Trade Union of Teachers in Romania (FSLI). The project is implemented within the Erasmus + program by the National Agency for Human Resources Development in Bulgaria (HRDC).]