Professional development of teachers is recognized worldwide as an important condition for high quality education. According to experimental data, pre-service and in-service training programs of preschool teachers are not always efficient, their interrelation with provisions for quality development in kindergartens is inconsistent. Developing potential of internship as a form of professional growth reduces deficiencies of programs focused on achievements of the kindergarten, on teaching technics without discussion of their worthiness and preschool values, perfunctory discussion, rigidity, organizational disadvantage. The authors discuss the criteria of effective internship. Programs work both to give specific knowledge and master pedagogical techniques, and, at the same time, to develop reflection. Programs support participants to adopt the cycle of pedagogical action. This research is aimed at selection of best practices of preschool education and analysis of their potential in internship. The research participants are Moscow teachers of 50 preschool groups. The groups, ready for internships, demonstrate significantly higher quality of education than the joint sample; however, they experience the lack of competences in work with adults and in development of their reflection. The internship programs elaborated by teachers from high quality groups show some deficiencies, namely, different topics interfere in one short-term program, the main focus is on object-spatial environment but not on interaction, participants’ outcomes are not embodied in any product. Best practices are interested in their own development as well as new sources of motivation. The authors have proposed internship to become a resource of development both for organizers and participants. Each position solves its own problems.