It isn't really the star which is good it's the child.
"A good gold star by your name" (Technique)
Transferred epithet - It is not the star that's good it's the child
"The inky tadpoles changed from commas into exclamation marks" (Technique)
Metaphor - Used to describe how the children "change forms" as they are growing up
"The classroom glowed like a sweetshop" (Nostalgia)
Simile - It links the classroom to the idea of somewhere you could expect to find pleasure/treats.
"A skittle of milk" (Childhood)
Reminiscing on childhood toys and the fact that you would get milk in primary school at break rime. They also stopped giving children milk in the middle of her primary school days.
"Skittle of Milk" (Nostalgia)
The memory of the milk bottles is expressed through the metaphor which links them to a childhood toy.
"The laugh of a bell swung by a running child" (Childhood)
A happy childhood memory as it is the end of a lesson.
"The laugh of a bell swung by a running child" (Nostalgia)
A happy memory as it is the end of a lesson.
"The classroom glowed like a sweetshop" (Childhood)
A sweet shop is one of the happiest and brightest places in childhood.
"The classroom glowed like a sweetshop" (Technique)
Simile - Comparing the classroom to somewhere filled with treats and happy memories of childhood.
"You could travel up the blue Nile with your finger" (Technique)
Metaphor - Following a metaphorical journey
"Mrs Tilscher loved you" (Nostalgia)
She felt secure and cared for in her teachers classroom. A motherly like relationship.
"Mrs Tilscher smiled and turned away" (Change)
Their relationship is changing. Mrs Tilscher is letting go, not rising to the challenge of explaining the answer to your question.
"Under the heavy sexy sky" (Change)
The children are changing from innocent children becoming sexually aware and how it feels like a rising storm.
"Under the heavy, sexy sky" (Technique)
Transferred epithet - The children are changing from innocent children becoming sexually aware and how it feels like a rising storm
"Inky tadpoles changed from commas into exclamation marks" (Change)
Tadpoles are a metaphor for growing up and changing from childhood to teenage hood and growing up.