The expression ‘children should be seen and not heard’ is an old English proverb, dating from the 15th century.

In the original form it was specifically young women who were expected to keep quiet. This opinion is recorded in the 15th century collection of homilies written by an Augustinian clergyman called John Mirk in Mirk’s Festial, circa 1450:

Hyt ys old Englysch sawe: A mayde schuld be seen, but not herd.