This article presents a case study on internationalization assessment. The international, intercultural and global dimensions at the school level are examined, focusing on the case of one particular secondary school in Israel. A novel, practical assessment tool is presented for the measurement of internationalization intensity and scope at the school level, based on systematic analysis of school websites and adapted from the existing assessment tool for higher education institutions. The results are verified by an in-depth interview with the principal of the focus school, confirming that the proposed tool can be easily used in large-scale studies. According to the assessment conducted, it was found that internationalization processes take place in each of the tested domains, although a large variation was found in intensity and appearance. This case study of an Israeli secondary school may serve as a point of departure to study internationalization in the secondary education system through the proposed comprehensive, reliable and easy to use school website assessment tool.