As Information and Communication Technology (ICT) literacy education has recently shifted to fostering computing thinking ability as well as ICT use, many countries are conducting research on national curriculum and evaluation. In this study, we measured Korean students' ICT literacy levels by using the national measurement tool that assesses abilities of the IT (Information Technology) area and the CT (Computational Thinking) area. A research team revised an existing ICT literacy assessment tool for the IT test and developed a new CT test environment in which students could perform actual coding through a web-based programming tool such as Scratch. Additionally, after assessing ICT literacy levels, differences in ICT literacy levels by gender and grade were analyzed to provide evidence for national education policies. Approximately 23,000 elementary and middle school students participated in the 2018 national assessment of ICT literacy, accounting for 1% of the national population of students. The findings demonstrated that female students had higher literacy levels in most sub-factors of IT and CT areas. Additionally, in the areas of strengths and weaknesses, the ratio of below-basic achievement among male students was at least two times greater than that of female students. Nonetheless, male students scored higher on CT automation, a coding item that involved problem solving using Scratch. Looking at the difference according to grade level, the level improved as the school year increased in elementary school, but there was no difference in middle school. When analyzing the detailed elements of middle school students, the automation factor of seventh grade students was found to be higher than eighth and ninth grade students. Based on these results, this study discussed some implications for ICT and computing education in elementary and middle schools.