In this article, the author explains the key differences among three kinds of instructionally relevant tests that can have a huge impact on what goes on in classrooms: "instructionally insensitive tests," "instructionally sensitive tests," and "instructionally informative tests." If educators understand the advantages and limitations of these three categories of tests, they can more effectively push for installation of the kinds of tests that truly improve instruction. The author also contends that in order for the No Child Left Behind goals to succeed, schools must use instructionally sensitive tests--tests that measure a modest number of important skills and bodies of knowledge and thus do not overwhelm teachers with a hoard of curricular aims too numerous to teach or test in the time available.