In a school that has more than one class for each (or most) grade(s), for example, 5A and 5B for 5th grade, what do you call the other (not yours) class and its students?
In Russian, it's literally a parallel class, but this meaning doesn't seem to be widespread in English, even though dictionaries just translate it like that.
As a Kiwi student, I'd call them my "year level" or "fifth form" or "year eleven"
Having worked in a high school, another name is "cohort" but that is specific to the teaching profession and wouldn't be used by the students themselves. The idea of a cohort covers everyone who started in the lowest year together, and those who joined the group as all these students moved up the year levels together.
Sometimes students might be delayed a year in a subject, or some get to jump a year, and they're still in the same cohort even if some of their work is at another year level.
In other words, a cohort is a loose grouping of students with similar social-developmental progress.
If you're looking at the idea of "parallel" as the core, then another school-jargon word would be "stream"
Imagine a hypothetical school with three subjects. A mandatory Mathematics subject,and students who can pick their other class subject. Everyone HAS to do maths, but half choose to do French and half choose Computers.
This means twice as many maths class teaching slots are needed. So there is a "French stream" and a "Computers stream" and that dictates which Maths class you're in.
In theory both streams are doing the same Maths contents, just at different times which matches your "parallel" point.
As a Brit I would say "the other class" or "the rest of the year" depending on how many classes their were.
Example
We got to go out for a special trip because our class won sports day, the rest of the year / other class had to stay at school and work.
I tried to do an n-gram but because of the vagueness of these phrases I realised it was meaningless.
Edit: in the UK our school time is named in years so you start in "year 1" and end at 16 in "year 11" . what you are called from 16-18 varies by institution.
When I was at Grammar School in England in the 1960s/70s, the other class in the year was indeed called the parallel class.
Thus the classes were labelled in the First Form as classes 1 and 1P. P standing for parallel. This continued, 2 & 2P for the Second Form up to the Fifth Form. The Fifth (age 15) was the last year of compulsory education in those days and was followed by the Lower Sixth then Upper Sixth Forms, which had no Parallel.
So in your question you state that parallel is not widely used in English, it used to be. The renumbering of classes as Year n came with the introduction of Comprehensive Schools and parallel became obsolete.
