In Enid Blyton and Frank Richards and similar books, "first form" to "sixth form" are the British equivalent of 7th to 12th grade in US and Australia.
At Westminster School in London, the original shell-shaped apse at the north end of the school gave its name to the 'Shell' forms (Junior School) taught there and the corresponding classes at many other public schools.
In Frank Richards' Billy Bunter series the Remove Class is the focus for all the stories, where the term is used as a synonym for Lower Fourth. They were pupils who had been removed (moved on an academic year) from the class described as the Shell.
Extract from Wikipedia below on UK schools, old and new.
|Key stage||Year||Final exam||Age||State funded schools||State funded selective schools||Fee paying independent schools|
|Early Years||Nursery (or Pre-School)||None, though individual schools may set end of year tests.||3 to 4||Primary||Lower||Infant||Various 'gifted and talented' programmes within state and independent schools.||Pre-preparatory|
|Reception (or Foundation)||4 to 5|
|KS1||Year 1||5 to 6|
|Year 2||6 to 7|
|KS2||Year 3||7 to 8||Junior|
|Year 4||8 to 9||Preparatory or Junior|
|Year 5||9 to 10||Middle|
A grammar school entrance exam, often the 11-plus
|10 to 11|
|KS3||Year 7||None, though individual schools may set end of year tests, or mock GCSE exams.||11 to 12||Secondary||Lower school||Senior||Grammar school and selective Academies|
|Year 8||12 to 13|
|Year 9||13 to 14||Upper||Senior (Public/Private school)|
|KS4||Year 10||14 to 15||Upper school|
|Year 11||GCSE||15 to 16|
|KS5||Year 12||Advanced subsidiary level or school-set end of year tests.||16 to 17||College||Sixth form|
|Year 13||A-Levels||17 to 18|
** End of Article