The Fourth R by George O. Smith

Jimmy discovered that he was admirably suited to the business of spotting. The "job turnover" was high because the spotter must be young enough to be allowed the freedom of the preschool age, yet be mature enough to follow orders.

The job consisted of meandering through the streets of the city, in the aimless patterns of youth, while keeping an eye open for parked automobiles with the ignition keys still in their locks.