Background: English language proficiency is considered a basic skill that students from different language backgrounds are expected to master, independent of whether they are native or non-native speakers. Tests that measure language proficiency in non-native speakers are typically linked to the common European framework of reference for languages. Such tests, however, often lack the criteria to define a practically relevant degree of proficiency in English. We approach this deficit by assessing non-native speakers' performance within a native speakers' framework. Method: Items from two English reading assessments--the Programme for International Student Assessment (PISA) and the National Assessment (NA) for English as a foreign language in Germany--were administered to N = 427 German high school students. Student abilities were estimated by drawing plausible values in a two-dimensional Rasch model. Results: Results show that non-native speakers of English generally underperformed compared to native speakers. However, academic track students in the German school system achieved satisfactory levels of proficiency on the PISA scale. Linking the two scales showed systematic differences in the proficiency level classifications. Conclusion: The findings contribute to the validation and international localization of NA standards for English as a foreign language. Practical implications are discussed with respect to policy-defined benchmarks for the successful participation in a global English-speaking society.