Garrison Keillor's amusing vignette from Lake Wobegon Days illustrates what this chapter is about. It is about the effects of testing on the curriculum, teaching, and learning. Its thesis is that testing is fast usurping the role of the curriculum as the mechanism of defining what schooling is about in this country. In recent years, it seems that the aims of education, the business of our schools, and the goals of educational reform are addressed not so much in terms of curriculum—the courses of study that are followed—as they are in terms of standardized tests. It is testing, not the "official" stated curriculum, that is increasingly determining what is taught, how it is taught, what is learned, and how it is learned.

Bloom's Taxonomy made its way into the pool of professional knowledge for educators despite criticism-sometimes quite harsh-on logical, philosophical, psychological, and empirical grounds. This last area is the subject of this chapter. Specifically, we review the empirical investigations of the hierarchical structure of the Taxonomy.

Can measurement really drive instruction and influence the curriculum? How does a test come to exercise power over curriculum and instruction? What is the nature of that power? This chapter explores these issues. However, to anticipate, the lesson of history is clear. Tests can be, have been, and in some places are the engines that drive teaching and learning. Is this a good thing? The answer depends on one's philosophy of instruction, curriculum, education, and testing. There are profound implications in this driving metaphor about the nature of instruction, curriculum, education, teaching, and testing.