This article offers new directions in measuring racial isolation in schools. The most widely used measurement approach is to examine the mean on the distribution of school percentage non-White across non-White students (the isolation rate) or the percentage of non-White students in schools with large shares of non-Whites (e.g., 90% or more) at a single point in time. Using data on New York City public school students, I discuss the complexity that is revealed when school officials and researchers consider the following three dimensions of racial isolation: between classrooms, over time, and among non-White students. (Contains 6 tables, 2 figures, and 6 notes.)