The purpose of this study was to assess the extent to which professional development programs within EARCOS member schools are consistent with research-based principles of effective practice. In addition, this study sought to identify the professional development opportunities that are being provided to EARCOS teachers. Finally, this study determined which professional development experiences teachers believe are most and least effective for their development. The literature review established a set of core features of effective professional development programs; content focus, coherence, durations, active learning and collective participation. The literature also highlighted a lack of evidence that schools/districts have successfully aligned their professional development programs with these core features. A survey was distributed to all faculty members working in EARCOS member schools. The International School Professional Development Inventory (ISPDI) was derived from a parent instrument, the International School Teacher Development Inventory (ISTDI). The ISPDI was designed to assess the extent to which international school teachers believed their professional development experiences were consistent with the core features outlined in the available research. The total number of completed surveys was 675, roughly 5% of the population. A factor analysis was applied to the ISPDI data outlining seven factors; active learning, support, and collaboration during instruction (ALSCDI), collaboration while planning instruction (CPI), content focus, coherence, onsite, traditional, and duration. Descriptive statistics were utilized to determine that teachers within EARCOS member schools perceive their professional development experiences to be well aligned with the identified factors, especially when compared with similar studies conducted in the United States. Further analysis highlighted that some organizational and individual level variables can impact a teachers perception regarding the effectiveness of their professional development experiences. Elementary teachers, and teachers working in non-profit schools reported higher alignment than secondary teachers or teachers working in proprietary schools. In addition, specialist teachers reported higher alignment than core area teachers. As teachers became more experienced, their perceptions of alignment with the identified factors also increased. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]