or to encourage them to work in traditionally difficult-to-staff schools. Teachers identified as highly skilled could also be used as a way of identifying instructional leaders who could then support other teachers and thus pass their skills onto other practitioners. We also point out that this benefit is one that is often claimed by programs that offer advanced-level certification in other fields, such as nursing or medicine: identification of highly skilled practitioners is the first step in realizing the benefits offered by a program that recognizes advanced practice. It is not necessarily a benefit in and of itself, but it serves as the foundation for other potential benefits. Moreover, the actual process of defining advanced practice can make a significant contribution to the field.
While the three benefits are interrelated, they differ in critical ways. For example, it is possible for an intervention to produce one of these benefits without providing the other two. In the context of a program like the NBPTS, it is easy to see that the program may produce the benefit of identifying highly skilled teachers without improving the teaching ability of the candidates as they go through the certification process or improving the quality of teachers throughout the education system. This result can occur if the certification process itself does not provide candidates with new skills or if the resulting certification is not used by the system in a way that changes what teachers are taught, who enters and stays in teaching, and who leaves, thus having no impact on overall quality.
Other interventions designed to improve teacher quality may focus entirely on one of these kinds of benefits and not at all on others. For example, inservice professional development is intended to improve teacher quality directly (Benefit 2) without providing a means for identifying highly skilled teachers (Benefit 1). However, increasing teacher pay is an intervention intended to improve teacher quality throughout the education system (Benefit 3) without directly identifying highly skilled teachers (Benefit 1) or directly improving the teaching ability of any particular teachers (Benefit 2).
Of course, improving the teaching quality of teachers throughout the system (Benefit 3) is presumably the ultimate goal of an intervention focused on teacher quality, and it is reasonable to assume that identifying highly skilled teachers (Benefit 1) or improving the teaching abilities of teachers going through a program (Benefit 2) are just two intermediate routes to achieving that ultimate goal. However, it is important to consider these two intermediate benefits separately, because their mechanisms for influencing teacher quality throughout the system differ. A certification program that improves the practices of teachers who participate in it (Benefit 2) will directly increase the quality of those teachers who participate, as long as the participants continue to be teachers, which will have a larger system impact to the extent that many teachers participate. However, a program that identifies highly qualified teachers without directly improving their