Excessive sodium intake leading to hypertension, stroke, and stomach cancer is mainly caused by excess use of salt in cooking. This study was performed to estimate the salt content in school meals and to compare differences in perceptions related to sodium intake between students and staffs working for school meal service. We collected 382 dishes for food from 24 schools (9 elementary, 7 middle, 8 high schools) in Gyeonggi-do and salt content was calculated from salinity and weight of individual food. The average salt content from elementary, middle, and high school meals were 2.44 g, 3.96 g, and 5.87 g, respectively. The amount of salt provided from the school lunch alone was over 80% of the recommended daily salt intake by WHO. Noodles, stews, sauces, and soups were major sources of salt intake at dish group level, while the most salty dishes were sauces, kimchies, and stir-fried foods. Dietary knowledge and attitude related to sodium intake and consumption frequency of the salty dishes were surveyed with questionnaire in 798 students and 256 staffs working for school meal service. Compared with the staffs, the students perceived school meals salty and the proportions of students who thought school meals were salty increased with going up from elementary to high schools (P < 0.001). Among the students, middle and high school students showed significant propensity for the preference to one-dish meal, processed foods, eating much broth and dipping sauce or seasoning compared with the elementary students, although they had higher nutrition knowledge scores. These results proposed that monitoring salt content of school meals and consideration on the contents and education methods in school are needed to lower sodium intake.