An effective teacher never leaves a key part of a lesson without checking to make sure there is an appropriate level of mastery before moving on to the next lesson segment. Teachers must monitor and assess student learning and then adjust their instruction to fit student needs, empowering themselves to do whatever it takes and for however long it takes to get students on board with what is being taught. The articles in this issue of Science Scope will be helpful to you as you monitor and assess student learning in your classes.