S.C. Code Ann. § 56-5-190

Every motor vehicle that complies with the color and identification requirements set forth in Section 59-67-30 and State Board of Education Regulations and Specifications Pertaining to School Buses which is used to transport children to or from public school or in connection with school activities, but not including buses operated by common carriers not exclusively engaged in the transportation of school students and vehicles having school bus markings temporarily removed or covered, is a "school bus".