Which does a school teacher tell his/her pupils in class, "Open your book to page XXX" or "Open your books to page XXX"?
I say "Open your books at page X", I might go on to say "Now turn to page XX".
Americans would say "to" page XX, as in the original sentence.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.