According to early childhood education scholar and leading expert on this topic, Lilian G. Katz, dispositions are a "pattern of behavior exhibited frequently... in the absence of coercion... constituting a habit of mind under some conscious and voluntary control... intentional and oriented to broad goals" that can be taught and caught through modeling. While this is the current buzzword in the evaluation of teacher performance, dispositions pose a problem for those seeking clean, lean assessment measures. One reason dispositions are so complex to understand is simply due to semantics. The National Council for the Accreditation of Teacher Education (NCATE) describes dispositions as the "professional attitudes, values, and beliefs demonstrated through both verbal and nonverbal behaviors as educators interact with students, families, colleagues, and communities." NCATE "expects institutions to assess professional dispositions based on observable behaviors in educational settings." The two professional dispositions explicitly recognized by NCATE are fairness and the belief that all students can learn. The National Board of Professional Teaching Standards does not define dispositions but expects that proficient teachers are able to employ the necessary "skills, capacities, and dispositions". The American Association of School Librarians refers to dispositions in its "Standards for Initial Programs for School Library Media Specialist Preparation" but does not define them. The AASL "Standards for the 21st-Century Learners," which comprise four learning strands each consisting of skills, dispositions in action, responsibilities, and self-assessment strategies, are the best example of dispositions for school librarians. While these dispositions are intended for students, they might also serve as specific dispositions of exemplary school librarians.