Personalized 100th Day Of School Smarter Party Youth Long Sleeve T-Shirt. Celebrate 100 days of school with this fun 100 days smarter Youth Long Sleeve T-Shirt - Heather for a school year milestone celebration. youth long sleeve t-shirt. Shoulder-to-shoulder taping. Youth: S(6/8), M(10/12), L(14/16), XL(18/20)