1) How can I shorten the word sixteen-year-old pupils?
sixteen-year-olds?
I need to include groups of students belonging to different classes. So I would like to identify them according to their age.
Yes, "sixteen-year-olds" or "16-year-olds" would work just fine.
To shorten the phrase "sixteen-year-old pupils" or "sixteen-year-olds" while still conveying the same meaning, you can use the term "16-year-olds". This shorter phrase represents students who are all sixteen years old.
When referring to groups of students belonging to different classes, you can specify their age range by saying "16-year-olds from various classes" or "16-year-olds across different classes". This clarifies that the students belong to different classes but are all the same age.
Additionally, if you want to refer to these students in a more general sense without mentioning their age, you can use terms like "students in different classes" or "pupils from various classes".