[gpm]

Toronto here, I think approximately I'd say first-sixth grade, and grade 7-12. Grade one just sounds wrong though.

[suddenlybananas]

Well, Toronto is ground zero for Americanization. First grade sounds super American to my ear, I'd never say it over grade one.

[wk_end]

Odd, I grew up in Toronto and Grade 1 sounds fine to me.

[fsckboy]

in the US, people tend to say "first grade", but if you say "grade 1" nobody would blink, people say it all the time, teachers, administrators, etc.