Hellman ironically uses as her title a quote from (and the name of) a poem by Longfellow. The first stanza is as follows:

Between the dark and the daylight,
When the night is beginning to lower,
Comes a pause in the day's occupations,
That is known as the Children's Hour.

The speaker goes on to describe how his three kids come down the stairs in an attempt to take him by surprise and interrupt his work in his study. Overall, the poem is gentle and positive in mood and gives a picture of domestic happiness.

Hellman's use of the title is appropriate, but it is also ironic in the extreme when compared with its original poetic context. In the play The Children's Hour, the plot centers upon a totally unexpected and destructive lie told by Mary, one of the children at a girls' boarding school, about the two women who run the school, Karen and Martha. Mary claims, falsely, to have witnessed the women having sex with each other. The play was written in the 1930s, and even when it was filmed in the early 1960s, gay and lesbian lifestyles were considered shocking and immoral by probably the majority of straight people. In the play and film, the parents of all the students immediately begin pulling them out of the school when the lie is relayed to them, and Karen and Martha's livelihood is destroyed. The two become pariahs, ostracized by the community and the world. It turns out that Martha does have romantic feelings for Karen, but she has never acted upon them and does not even reveal them to Karen until the end of the film version, shortly before Martha commits suicide by hanging herself. In all, the story illustrates the destructive results of hatred and prejudice against gay and lesbian people in that time.

The allusion to Longfellow's poem is ironic because the situation in Hellman's play and its filmed version is the complete opposite of the gentle domestic scene in a work by one of America's most conservative and uncontroversial poets. But in the play, "the children" are having their hour, because Mary's lie (abetted by one of the other girls whom Mary blackmails into supporting her story) is effective in destroying the lives of the two headmistresses she hates.