Across Europe we can observe the reinforcement of monolingual education policies, despite increasing multilingualism. Recent research has shown that the emphasis is on language proficiency in the socially dominant language. This is viewed as the key to educational success. The use of other languages or linguistic repertoires is not valued in educational policies, nor in educational practices. These monolingual policies and practices affect the assessment of pupils' (language) proficiencies and practices. Pupils who do not (solely) speak the school language at home also take content-related tests in e.g. mathematics or science in a language they are often not yet familiar with. In this paper, we discuss why and how this imposes limitations on test results and may result in unfair disadvantage. We first present alternative ways of assessing multilingual pupils for purposes of large-scale testing which can be explored in future research. Second, we focus on the potential of classroom-based and learner-oriented multilingual assessment. We conclude the paper by introducing the concept of Functional Multilingual Assessment For Learning and argue that this can be a powerful means to overcome some of the limitations in the assessment of multilingual pupils who are still in the process of learning the language of instruction.