This article is Part 3 of a three part summary of selected articles from the journals of the American Association of School Librarians (AASL) over a period of thirty-five years from 1972 to 2007. This three-part series in the April, May, and June (2009) issues of "School Library Media Activities Monthly" ("SLMAM") illustrate the evolution in professional thinking about the instructional role of the library media specialist and the library media center. Three major trends emerge from all the instructional issues depicted in the professional association journals. These three major trends are covered in each part of this three-part series. Part 1: From Teacher-Centered to Student-Centered; Part 2: From Library-Focused to Information-Focused; and Part 3: From Access-Measured to Evaluation-Measured. Each is based on the direct observations and conclusions of the article authors. Part 3 focuses on a new level of measuring the effectiveness of library media specialists and library media programs. The modern library media center, at one time evaluated by the high quality status and extensive quantities of its holdings of multimedia resources, is now subject to evaluation by the effectiveness of information used by teachers and students. The ability of students and teachers to effectively use the library media center is based on valid evidence, personal and audience understanding, and clear presentation. [For Part 2, see EJ837443.]