Comparing fractions

It’s the SATs that brought it on.
It’s six-fifteen as I lie in bed
but sixty years ago in the classroom.
I’m cutting up the party cake –
the one I’ve drawn with coloured chalk –
and turning the minute hand on the wooden clock.

Halves, quarters, eighths, thirds, sixths,
drawn, compared, added and subtracted.
Tomorrow we may multiply and divide
but sevenths will not be used …
Ever tried cutting a cake in seven?

Later, with the older ones: three sevenths, four ninths:
which the greater? Oh Sir!
Whoever saw a ninth? Or a seventh, come to that.
Seven days in the week; a day is a seventh.
That takes us through the year. At the very end

there’s an awkward little bit: not a proper fraction –
celestial malfunction, cause of endless flap
diabolic in its lack of vulgarity.
Some say lucky seven. The luck of the devil say I!

Incidentally, in my dream the following night I was designing a correspondence course in Calculus. Where will it end?