The first year of the sixth form in English, Scottish and Welsh schooling. This is the stage of school where students are no longer legally required to be there.
Year 12 used to be considered a doss year where you could lie around playing pool and table football for a year. It was the first year of A levels, and the exams weren't until year 13. This system changed in 2001 - AS levels were introduced, and year 12 is now considered to be the hardest year of school.