I incorrectly assumed their snacks would be kept in their individual backpacks or cubbies until snack time.
No cubbies in his classroom. The preschoolers have small school-provided tote bags that hang on hooks. They're just big enough to hold a file folder. I haven't seen any of his classmates with separate lunch-sized bags. Snacks (I presume) are removed from their tote bags and put into the communal snack bin. The daily "snack helper" child hands them out at snack time.