The focus of the article is on Phase I of an American-Slovenian collaborative research project that was aimed at investigating effective classroom teaching-learning performances. The international project involved Dowling College and its first Professional Development School (PDS)--the Belmont Elementary PDS--and the University of Primorska at Koper and its partnering elementary school, the Dr. Ales Bebler School. As part of the first phase of the project, a video-based action research study was conducted to analyze and assess videotaped lessons taught by American PDS teacher candidates and Slovenian student teachers. Based on the findings changes were made to aspects of the teacher education programs and their respective school-university/college partnerships. For purposes of this article the authors present an overview of Phase I of the project, a working conceptual framework for the project, and selected findings of the Phase I video-based action research study. (Contains 5 figures and 1 note.)