Despite their widespread use, letter grades do not provide useful long-term pictures of student progress because they relate only to short-term success on defined bodies of taught content. If school assessments in the 21st century are to contribute to improved learning and better outcomes for all students, then a change in approach is required. Assessments must be designed for the fundamental purpose of establishing and understanding where learners are in their long-term progress in an area of learning at the time of assessment.