This paper provides an analysis of how Swedish 15-year-olds perform on the high-stakes national assessments in geography. It explicitly addresses which item characteristics produce differential item functioning (DIF) in favor of boys and girls respectively. The findings show that DIF occurs in favor of girls in items with constructed response and primarily with content on the social dimension of sustainable development (SD), while boys are more favored by content outside the field of SD. The conclusions drawn are that content that reaches higher levels of Bloom's taxonomy favors girls, especially when the subject content concerns SD. This is important when analyzing the teaching and examination of sustainability issues in school.