This study investigates the perceptions and differences between kindergarten and elementary school teachers regarding the importance and performance of school readiness for young children. The subjects of the study are 114 kindergarten teachers who currently teach 5-year-olds or have taught them within the last 3 years and 106 elementary school teachers who currently teach first graders or have taught them within the last 5 years. The research tool was modified to fit the purpose of this study, drawing on Bang (2013) and Lee (2005). The collected data were analyzed using frequency and percentage, maximum and minimum values, mean and standard deviation, and t-tests. This study yielded the following results. First, significant differences were found in how kindergarten teachers and elementary school teachers perceived the importance of young children's school readiness in the overall and subdomains except academic skills, with elementary school teachers placing a higher value on it. Second, significant differences were found in how kindergarten and elementary school teachers perceived the performance of young children's school readiness, in general and subdomains, with kindergarten teachers believing that more young children could perform those than elementary school teachers. These results imply the need for a two-way connection between early childhood education and elementary education, thus redefining the role of early childhood education and strengthening cooperation with families.