We’re sending my rising K’er with the same little LL Bean backpack that we’ve used for 5 years as a diaper bag then preschool bag. It fits his body and I bought it with the goal to use it until he needed something larger for books, etc. I suspect we’ll be getting a larger version of the same pack in 3rd / 4th and then 9th. FWIW, his school doesn’t have homework or textbooks or iPads, and winter outdoor clothes / rain clothes stay at school.