Note that ‘score’ is originally from incising a mark - literally scoring a mark in the side of a tree, in order to count. One score is one mark. Multiple scores are multiple marks.
A ‘score’ is thus a singular item – for example, the total that a student gets in response to one test.
Scores–the plural–is a collection of results, either within one test, or the totals of multiple tests. Multiple ‘marks on the tree’.
- If there is one number, or result, ie 80 - use score
- For multiple numbers, or results, ie 10, 30, 80 - use scores.
- I scored 17 in my test (singular) I had 1 score
- My scores for the 3 tests were 18, 15, and 3 (plural) I had multiple scores.
On top of that, you have ‘the student’ or ‘students’ - ie, whether ‘students’ is singular or plural. I think that is what is confusing you.
Start with scores - is it plural or singular - and then look at student or students - to sort that out.
If ‘score’ is singular - i.e. it’s just one number, then use:
They get the comment ‘study hard’ if their score is below 40
If ‘scores’ is plural - i.e. each student gets multiple numbers as a result, then use:
They get the comment ‘study hard’ if their scores are below 40
If you need to or want to differentiate:
If ‘scores’ are varied i.e. they have several numbers, and any one of said scores falling beneath 40 causes the ‘study hard; message then use:
They get the comment ‘study hard’ if any one of their scores are below 40
‘scores’ refers to ‘all their scores’ here, so it is plural.
If ‘scores’ are varied i.e. they have several and the amalgam of said scores dropping beneath 40 causes the ‘study hard’ message then use:
They get the comment ‘study hard’ if their amalgamated score is below 40
note: there is one score i.e. 1 number. So ‘score’ is singular here.
Etymology and Meaning
Score from Old Norse skora ‘make an incision’ and skor ‘notch’. Interestingly, skora also means 20 in old Norse which is why we call 20 ‘a score’. As in ‘3 score years and 10’.