Education systems worldwide have shown much interest in "21st Century Competencies." In response to the call for better assessment of these competencies, we draw on a 4Cs framework (Communication, Collaboration, Creativity, and Critical Thinking) and develop the 21st Century Competencies Scale-4C on a sample of 5857 Grades Four to Nine Chinese students. The Scale demonstrates good validity and reliability, yet statistical variance exists across the urban and the rural subsamples. Our discussion revolves around rural-urban disparity. Our findings provide insights into policy, practice, and research regarding 21st Century Competencies that account for sociocultural dynamics within student populations. These findings may have implications for understanding 21st Century Competencies elsewhere.