Personalized 100 Days Of School 100th Day Party Youth T-Shirt. Cute 100 days of school Youth T-Shirt - White 100th day party celebration apparel. Let the good times roll in a durable T-Shirt that takes kids from school to play in an amazing array of colors. 5.0 oz., pre-shrunk 100% cotton. Seamless 1x1 rib collar.