Duffy conveys a childhood idyll in the first two stanzas. The classroom is a place of colour, safety, learning, delight. All elements of a happy childhood. In the second two stanzas, the child is exposed to the outside world and the knowledge this brings.
Duffy mentions Brady and Hindley, the infamous Moors Murderers, but they are "faded" in the positive world Mrs Tilscher creates. This conveys how in childhood the horrors of the adult world often do not have an impact, as it is a time of innocence and make believe. It is also short-lived as the second half of the poem confirms when the children begin to grow up.
The poem charts the speaker moving from childhood to early adolescence. The secure, innocent world of Mrs Tilscher's class is interrupted by the outside world. A "rough boy" tells her how she was born and gives her knowledge she is not ready for.
The final stanza depicts a sexual awakening as Mrs Tilscher 'turns away', leaving the child to explore her new feelings independently. She is growing up and cannot go back to her childhood of innocence and safety any more. She has to move forward, push the limits and handle the storm that looms on the horizon.
This poem would pair well with Originally as both explore childhood and growing up. While In Mrs Tilscher's Class focusses on the joy of primary school that is closely followed by adolescence, Originally looks at the impact of physically moving country as a child and having to fit in as well as moving from childhood into adulthood.
The both also deal with powerful memories. In terms of language to conjure place, the use of senses and the portrayal of character, you could also pair it with almost all of the other poems.