As Mrs. Oublier sees it, her classroom is a new world. She reported that when she began work 4 years ago, her mathematics teaching was thoroughly traditional. She followed the text. Her second graders spent most of their time on worksheets. Learning math meant memorizing facts and procedures. Then Mrs. 0 found a new way to teach math. She took a workshop in which she learned to focus lessons on students' understanding of mathematical ideas. She found ways to relate mathematical concepts to students' knowledge and experience. And she explored methods to engage students in actively understanding mathematics. In her third year of such work, Mrs. 0 was delighted with her students' performance, and with her own accomplishments.