In these complicated new times, many new teachers begin their careers in urban and other schools with increasingly diverse student populations. And as people know, many new teachers leave those schools--and some leave teaching altogether--after just a few years in the field. In today's world, policy makers, politicians, educational leaders, the general public, and parents expect a great deal from teachers. This article explores what teachers really need to know to teach effectively in these new times when there are extraordinarily high expectations for teachers. In fact, many people around the world now agree that teachers are among the most important, if not the single most important determinant of students' learning, as well as the linchpins in educational reforms of all kinds.