Something that I noticed is that Canadians often use "Grade X", while Americans prefer "Xth grade". For example, Canadians would use "Grade 9" rather than "9th grade," while Americans use "9th grade" rather than "grade 9." (Source)
Although Canadians aren't the only ones to use "Grade x", they use it an overwhelming 97% of the time, which is higher than all other countries afaik (Source). As a result, a rule of thumb is that when I hear "grade x" in certain grammatical contexts, I can assume the speaker is Canadian and the assumption is usually true.
I tried to find some documentation on this phenomenon, but I found nothing. What might be the origin of this regional distinction?