This dissertation examines a vital catalyst in the globalization of education: international assessments--that involve testing and rankings--of student achievement in academic subjects. Nearly all high-income countries participate in international assessments such as Trends in International Mathematics and Science Study (TIMSS), Progress in International Reading Literacy Study (PIRLS), and Program for International Student Assessment (PISA), and participation is also growing among low-income countries. Empirical research on these assessments, however, is less extensive than what might be expected. Three broad questions guide this dissertation: (1) How did international assessments become a rationalized educational practice? (2) Why did countries choose to participate in international assessments? (3) How international assessments are engaged in public discourse at the local level? Using a multi-method approach to address these questions, I draw on a variety of data sources: an extensive array of primary-sources materials from archives from North America and Europe, interviews with 45 key actors from 15 countries in the field of international assessments, an original data set that includes 130 independent nation-states and their record of participation in international assessments from 1964 to 2012, and newspapers articles from Israel to examine the integration of international assessments in public discourse. The analysis shows three key patterns. First, the field of international assessments emerged from a loose network of scholars oriented toward education research and later transformed into a set of organizations that emphasized accountability of education systems. This transformation was driven by two mechanisms: resources and international discourse about education. Second, the transformation toward educational accountability is implicated in the diffusion of international assessments worldwide. In the early stages of international testing, a country's embeddedness in Western scholarship affected participation in international assessments. Subsequently, when the field emphasized accountability, a country's embeddedness in world society affected participation in international assessments. Third, local actors' engagement with international assessments--via processes of interpretation and appropriation--further legitimized international assessments. Taken together, these patterns suggest that the institutionalization of policy scripts--such as international assessments--is driven by dynamic processes that take place at the global and local level. [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.]