One of the greatest challenges of teaching stems from the lack of immediate, accurate feedback. The student who walks out of your classroom tonight shaking his head and muttering under his breath about algebra may burst into class tomorrow proclaiming his triumph over math, and thanking you for the previous lesson. There is no way to predict precisely what the long-term results of our work will be. But if we have a sense of purpose informing our choice of strategies and materials, and we try to cultivate expectations of success for all our students, we will be less likely to dwell on that unpredictability, choosing instead to focus on what we can control, and trusting that thoughtful preparation makes good outcomes more likely than bad ones.