When it comes to shoes, GS stands for "Grade School" and refers to a range of shoe sizes that are designed to fit a childs foot at grade school-age. The GS shoe sizes start from 3Y and go up to 7Y, and they are not limited to grade schoolers, as adults can also wear them. GS shoes are gender-neutral and appropriate for school-going children. The GS size is not a specific shoe size but a range of sizes likely to fit grade school students. GS-sized shoes are great for adults with relatively smaller feet who need shoes with a snug fit. It is important to note that GS sizes do fit on the smaller side, so it is recommended to purchase a half size up.