Clothing plays an important role in the performance and movement of the human body in different age groups so the development of clothing sizing system is the best way to provide the best suitable size in clothing design. The current project is the fourth step towards the overall objective to develop a clothing sizing system for Libyan children based on anthropometric body measurements of Libyan school children. The aim of the current project is to examine anthropometric measurements for female students in grades seven, eight and nine in the basic education stage, to collect body measurements of school children in Benghazi and analyze those using simple statistical methods to understand the body ranges and variations present for students in the three grades to develop sizing system of these grades. Twenty body dimensions were measured for each student to develop clothing sizing system. The measurements were gathered from a total of 180 students (children of age 12 to 14 years old, females) from four schools in Benghazi. The anthropometric data were analyzed using Minitab program. ANOVA tests were used to identify differences between age groups. The results showed that there are differences between most of the body measurements except the head circumference, shoulder to shoulder length, shoulder to waist length, front body width, back body width, knee height. These differences were taken into account when developing sizing system. Pearson correlation coefficients analysis was carried out to determine the interrelationships between the various body measurements. From these findings it may be concluded that the weight, chest circumference, is very strongly correlated with some other dimensions. The mean values and the standard deviation were used for creating size steps for the size chart. Three kinds of sizes were identified: L (large), M (medium) and S (small).