Art Center College of Design in Pasadena is really the best school for concept art. A master’s degree won’t matter at all in terms of the actual quality of your work; actually most MA / MFA programs are just watered down money makers for schools, you won’t get much out of a master’s program for concept art, even if one does exist. An MFA only matters if you want to teach at the college level, or a MAT for the high school level. If you really want to work as a concept artist, be aware that it’s an extremely small and competitive field and that the best ones are coming out of Art Center.