[virtualwhys]

In the US, for schools that use this form of grading, it means your senior year; 3rd form is freshman year and so on.

We tend not to have a 13th grade, and when that does exist, a PG (post grad) is generally there because they excel at a particular sport.

[jonp888]

In Britain the first high school graduation happens after 11th grade; attending sixth form is optional and is primarily done by students intending to study at University. In these years you specialise in a couple of subjects relevant to your intended course of study, and for university you apply and are accepted for and study exclusively one subject from day 1.

So arguably the US equalivalent is the freshman year of college.

[billyoyo]

Just to clarify this as well, while sixth form (17~18 years old) is optional in the UK, education is still compulsory until you're 18. you have the option to do this at an apprenticeship or skills based school but lots of people do just default to a levels.

[kaladin-jasnah]

I guess some people in the US call someone beyond their 12th grade in high school, or fourth year in an undergraduate program a "super senior."

[TylerE]

I've literally never heard or read that. So I would say no.