Student or Learner
What's British for a grader? He's a fifth grader.
This reminds me of something I've been wondering for some time.
In the Harry Potter books, school staff address the students by the year number, in this way: "First-years, come along" or "Third years, assemble in the Great Hall", instead of "first-year pupils" and so on. Is this common practice in the UK?
When the (for example) 11-12 year group at secondary schools was called 'First Year' or 'First Form', the pupils were frequently referred to as 'first years' or 'first formers'. Now both the year group and the pupils are known as "Year Seven".
Singular: "I'm a first year/first former/year seven."