What is "ouvrez vos cahiers" in English?
This is my son's homework
Open your [speaking directly to a group]
And it sounds like your son might need to do that
a bit more often for his French class
Wonder why she's asking questions on a Spanish forum. Shouldn't she at least know which language her son is studying?
This is French , how about going to a French dictionary.
Please note that this is a language forum. Proper grammar, including correct spelling, capitalization, and punctuation, is required. - Greg-Hahn
Please remember this is a learning site, anyway, as it seems, your son is learning French, which might come as a shock to you as you are posting this on a Spanish-English site.
Gus is correct, it is French. It means "Open your note (exercise) books"
In most cases just using cahiers would mean your notebook, but it is short for cahiers pour écrire or cahiers à spirales. Most of the time it is simply called cahier.
An exercise book, however, is usually referred to as cahier d'exercices or cahier écolier.
It would probably depend on what the teacher has been referring to as cahier since the beginning of the semester.