Over the last 25 years, we have accumulated considerable evidence that assessment can improve, as well as measure the results of, education. However, we have also learned that using assessment to improve learning is much more than adding a few “quick fixes” to what teachers do. Rather, harnessing the power of assessment to improve learning involves a number of major shifts in how we think about education and policy, and, without these shifts, the potential of assessment to improve learning is likely to remain unrealized. The shifts that seem to be most relevant to the current policy environment in Europe are summarized below.