read from the same hymn book

To have the same understanding, thought process, or amount of knowledge (about something) as someone else. A less-common variant of "sing from the same hymn book." We all need to be reading from the same hymn book before we try to present this idea to the boss. I think it would help if both parents attended the presentation. That way, you'll both be reading from the same hymn book when it comes time to implement what we talk about.