Question

たこ

Only with industrialization and the appearance of a middle class and formally organized schools did childhood become a clearly definable period of time.
didがよく分かりません、、、

Answer 1

Ryu

まず、文頭に否定を表す節や語があったら
倒置を疑ってください。
大雑把にいうと
(否定語+疑問文の形)
になるので助動詞のdoの過去形であるdidが
あらわれています

たこ

元の文章は、childhood become a clearly definable period of time only with industrialization and the appearance of a middle class and formally organized schools.ってことで合ってますか？