Why does the poet leave a dash at the beginning of the first stanza of the poem?

Wordsworth had a distinct style in which he tried to inspire feeling in the reader by using visual markers to control how the reader read the poem. The poem “There was a Boy” in Lyrical Ballads thematizes this concept, featuring a boy who experiences “pauses of deep silence” in nature. This theme of silence is developed in Lyrical Ballads as something which brings men into communion with other men and nature. Wordsworth thus showed through his poetry the profound effect of a pause on the person experiencing it, which a poet can himself replicate by representing pauses on the page. Wordsworth himself used dashes to bring the reader to pause, bringing the reader to pay closer attention to particular lines and, in turn, have a closer sympathy with the narrator's perspective in the poem. In the first line of “We Are Seven,” we can read the elongated dash as something which, by bringing the reader to pause before reading the first line, dramatically sets it apart from the other lines. It is a dramatic opening, bringing us to pause and focus on three simple words: “A simple Child.” The simplicity of the phrase alone, demarcated from the other three lines, emphasizes through style what the narrator is describing: a simple child. Similarly, the second pause at the end of the third stanza is a visual marker which makes us pause when reading it, bringing a poetic emphasis to that line. Even though the poem is written in trochaic meter and it would be easy to rush through that last line because rhythmically it is undifferentiated from the other three lines in the stanza, the dash brings us to pause and revel in the beauty the subject of the poem is describing to us rather than speed through the poem.