https://en.wikipedia.org/wiki/Domestication_and_foreignizati...
https://en.wikipedia.org/wiki/Domestication_and_foreignizati...
If you use "freshmen" to describe them, you get the "new at school" aspect, but viewers will get the completely wrong idea about their age. If you use "juniors", you get the age aspect right, but their role and social standing at school would be completely off.
So in a case like that, domesticating the translation simply doesn't work, you'd get super confused as a viewer if you use American high school terms. So you have to foreignize it, you have to call them something else, and you have to make up new terms when translating the various Norwegian derogatory terms for first-year students that exist.
I'm glad you didn't use the word. It would seem really out of place.
In England, we just said "6th year" (cf Harry Potter), "lower sixth" or "Year 12", depending on how old fashioned the school was.
I ended up using "first-year", "second-year" and "third-year", and "firstie" for when older students were looking down on them.