It took me quite awhile to find just the brand of backpacks I wanted to carry, but Dabba Walla's were just exactly I was looking for.
Each one features a fun, eye-catching design made of lightweight and washable neoprene. The straps adjust via a D-ring on the inside of the bags, so there are no straps or plastic pieces hanging down and getting in their way. I think they just scream, "Take me to pre-school!"
80% Neoprene, 20% nylon.
Machine wash, air dry.