As science education moves increasingly in the direction of teaching to standards, teachers call for classroom assessment techniques that provide a richer source of “rigorous and wise diagnostic information.” Student-to-student comparisons and single grades are no longer enough, and here the authors describe a new type of criterion-based assessment to track individual learning trajectories. It can be embedded in the curriculum, easily used in the classroom, customized by grade level, subject area, standard set, and controlled by the classroom teacher.