Source identified1
“A child should not be ordered about, but should be just as courteously addressed as a grown person in order that he may learn courtesy.”
Key argues that respectful treatment is itself part of teaching respectful conduct: adults model the courtesy they expect children to learn rather than relying only on commands.
Source note: The Century of the Child, Chapter III, “Education,” Francis Maro translation revised by the author, Project Gutenberg #57283, printed page 130. The sentence belongs to Key’s early-twentieth-century reform pedagogy; nearby prescriptions are historically situated and are not imported into this collection as current child-safety or clinical guidance.