The increasing emphasis on testing in U.S. schools is a consequence of perhaps the most profound change in American education in modern times — the shift in focus from teaching to learning. When education systems concentrate on teaching, the emphasis is on the process of instruction, measured in the length of time students are exposed to teaching. (Think, for instance, of the 180-day school year.) Time is the constant; all students are expected to learn the same amount of information in the same period of time. (source Los Angeles Times)