Wikipedia:
The Education Specialist, also referred to as Educational Specialist, Specialist in Education, or Ed.S., is an advanced terminal degree in the U.S. that is designed for individuals who wish to develop advanced knowledge and theory beyond the master's degree level, but may not wish to pursue a degree at the doctoral level. Advanced programs beyond the master's degree are designed to provide the necessary background and professional expertise for students planning to go into university teaching, supervisory or leadership roles in post secondary schools, curriculum planning, consultant work, or similar positions.
Since the course work in an Education Specialist degree is at the doctoral level many schools will transfer the credits earned directly into a doctoral degree (Ed.D, Doctor of Education).