The speaker in Blake's, "The Chimney Sweeper," from Songs of Innocence, is a child and a bit naive. Born of poor parents, he was sold into virtual slavery and now is a chimney sweeper, a job that filled one's lungs with soot and usually resulted in early death.
The treatment of these children is made to seem okay in the poem narrated by the child, since salvation awaits them in the form of angels. The child speaker, as well as Tom Dacre, buy into this faulty reasoning. The poem is presented in an innocent manner by an innocent narrator, and it is left to the reader to determine the injustice of their situation.
In the companion poem of the same name in Blake's The Songs of Experience, a child chimney sweeper is again present in the poem, but this time the speaker is an adult passing by the child who asks him where his parents are. This child faces the same situation the previous child faces, but this one is intelligent enough and aware enough to see society's line of thought as faulty: he knows better than to naively accept that hope for a future reward makes the way sweeps are treated okay.
Thus, a child can be experienced, too. Age is not the only issue.
Both poems feature misused and abused children. The difference is that the second child knows he's being misused and abused. Blake is interested in perceptions, and in these poems we see two opposite perceptions of the same situation.
The chimney sweeper in William Blake's poem resonates with his poem about the city streets of London and represents, along with the girls sold into vice, the voice of the previously [pastoral peasantry tempted into London by the need for food and shelter for their families. The streets were not paved with gold however, even after the Industrial Revolution, as the new wealth generated was equally spread. The rich just got richer by exploiting the poor through cheap labour and the poor got poorer and died young. Their voices ring out in the poem as a scream against humanity particularly a perceived uncaring establishment and church. These organisations could have been doing a lot more to speak up for the poor.