Assessment of learning outcomes and competences is a major part of everyday class-room practice. The shift to competence-based learning and teaching over the last decades has resulted in changes of attitude and approaches towards assessment. Whereas tradition-ally assessment was mainly used to make summative judgments of student achievement, it has increasingly become a tool for learning. Formative assessment identifies progress and gaps in student learning to point to learning needs and adapt teaching accordingly. Rather than assessment of learning, it is assessment for learning. Assessment differs according to context and purpose. Multiple types of assessments are needed to form a more comprehensive picture of what students know and are able to do, and what their learning needs are. The difference between various forms of assessment, including summative and formative is how the evidence of student learning is used. While standardised assessment tools allow comparison on different levels (e.g., across subjects and teachers), student-centred (formative) assessment can build students’ skills for self-assessment and learning-to-learn, while also raising levels of achievement. Bridging theory and practice is key to aligning curricula and assessment. Top level steering and theory might differ substantially from what teachers apply in the classroom, es-pecially in systems with high school autonomy. Involving teachers in designing assessment will help bridge the theory-practice gap and ensure that assessment practice links to curricula content.