When parents these days hear the old saying “The jobs of tomorrow haven’t been invented yet,” they tend to add, “so my child had better learn to code.” As software has redefined a range of industries and professions, many parents are rushing to make sure their children learn the building blocks of computer programming.

Toy and game developers have responded. One recent entry—and, for young children, one of the best—is Osmo Coding, by Tangible Play Inc. Using plastic bricks that represent computer commands, children arrange...