The PsyS is a post-masters specialist degree in psychology, and is usually specialized in school psychology. The PsyS degree is a four-year program, the first two years earning an MS (usually in general psychology, developmental psychology, or school psychology) and the last two earning the specialist degree. As a whole, the degree includes three years of course work (including practice) and a one-year internship.
This degree is primarily designed for practicing in the school setting, although after three years of post-grad field work one can operate in private practice. This degree is not designed for those who would like to attain a PhD, however, it is possible to switch over some credits in search of an EdD after the PsyS is completed.
In addition, this degree is used in clinical psychology. In this application it is a two-year post-master's degree. This degree entails two years of course work including a clinical practicum and is often the first part of a four-year PsyD degree. The PsyD is a degree specializing in clinical psychology training, in lieu of the more research based PhD.