Personalized Happy 100 Days Of School T-Shirt. Additionally, our Happy 100 Days of School Design is not limited to just kids and teachers. It can also be a fantastic costume option for women on the 100th day of school. Wardrobe essential for looking good, 24/7. 5.0 oz., pre-shrunk 100% cotton. Seamless 1x1 rib collar. Shoulder-to-shoulder taping. Double-needle stitched sleeves, bottom hem and front neck. Note: greys are a cotton/polyester blend.