Asserts that Dewey's proposal that rich, engaged learning requires teachers to "psychologize" their subject matter, remains timely in today's education, especially given recent mathematics and science curricular reforms. The article contrasts his proposal with more subject-centered reforms, explaining how teachers must understand students' subject-relevant experience and how teachers can combine promising "big ideas" with sensitive analyses of students' experience to transform subject matters, especially for lower achieving students. (SM)