Assessing students is a key part of teaching a language. Placement tests are used to help teachers set up learner groups that can work together, and to inform decisions ranging from choosing the most suitable coursebook to devising the teaching content to suit a particular group of students. The workshop explores what functions a placement test must fulfill, what essential qualities a valid, reliable and practical test must have — and how these qualities can be ensured. It also looks at how the Oxford Online Placement Test empowers teachers to understand their learners.