The paper explores the relationship of the global and the local assessment discourses as expressed by Programme for International Student Assessment (PISA) test items and school-based examinations, respectively. To this end, the paper compares PISA test items related to living systems and the context of life, health, and environment, with Greek school-based biology examinations' test items in terms of the nature of their textual construction. This nature is determined by the interplay of the notions of classification (content specialisation) and formality (code specialisation) modulated by both the linguistic and the visual expressive modes. The results of the analysis reveal disparities between assessment discourses promoted at the global and the local level. In particular, while PISA test items convey their scientific message (specialised content and code) principally through their visual mode, the specialised scientific meaning of school-based examinations test is mainly conveyed through their linguistic mode. On the other hand, the linguistic mode of PISA test items is mainly compatible with textual practices of the public domain (non-specialised content and code). Such a mismatch between assessment discourses at local and global level is expected to place Greek students at different discursive positions, promoting different types of knowledge. The expected shift from the epistemic positioning promoted in Greece to the one promoted by PISA could significantly restrict Greek students' ability to infer the PISA discursive context and produce appropriate responses. This factor could provide a meaningful contribution in the discussion of the relatively low achievement of Greek students in PISA scientific literacy assessment. (Contains 1 note, 4 examples, 2 figures, and 4 tables.)