GS in shoes stands for "Grade School," which refers to the size of the shoes in relation to an average kids shoe size. The GS shoe sizes start from 3Y and go up to 7Y, and the main difference between them is their quality and pricing. The GS size is not a specific shoe size but a range of sizes likely to fit grade school students. While GS shoes are designed for children, adults with small, slender feet can also wear them. GS-sized shoes are great for adults with sizes UK 3-6, as they are practically the same and sometimes cheaper. If you are an adult purchasing a GS sneaker, it is advisable to take half a size up. GS shoes are not limited to grade schoolers, and anyone with relatively smaller feet who needs shoes with a snug fit can wear them.