This booklet is intended to help school personnel, parents, students, and members of the community understand concepts and research relating to achievement testing in public schools. The paper's sections include: (1) test use with direct effects on students (test of certification, selection, and placement); (2) test use with indirect effects on students (making judgments concerning the quality of an instructional program or the teaching staff, or to validate the worth of a curriculum or specific practices); (3) criterion-referenced tests (tests that provide an estimate or approximation of how much a student knows about a subject); (4) technical features of tests (test validity, setting standards, test reliability, and test bias); (5) test use (principles to guide school use of tests); and (6) activism and testing (a strategy to help teachers, school administrators, and parents question information not conveyed in common lanugage). (PN)