Answer:
Masters of Special Education- This title originates from the Masters in Education with the specialization in Special Education. It is abbreviated as M.Ed. A logical thought would be M.Sp.Ed. but it is not recognized as such. I have my Masters of Special Education and that is how it is abbreviated on my degree.
I have a masters degree in Special Education (focus area: emotionally disturbed) and 90 additional post graduate hours in special education. I taught special for 28 years. I have always abbreviated it like this: Forrest298, Ma.ed. However, many states use different abbreviations for disabilities. Therefore, I would not be surprised if different states used different abbreviations concerning teacher credentials.