We were just in a first grade classroom where we witnessed this very thing! One partner was obviously a strong reader, sharing a book with a lessor skilled student. Every time the struggler paused, his partner "helped" by submitting the correct word immediately.
We recommended the 'Coaching or Time' technique.
As partners read together, if the reader pauses, partner two remains silent, but mentally springs into action. He silently and slowly counts to 3 (taking 3-4 seconds to reach 3), while raising a finger for each count. When he reaches three, he says, "Would you like coaching or time?" If partner one says "time", partner two waits patiently, but is thinking about strategies that may help if partner one changes their mind. If partner one says "Coaching", partner two offers a strategy that may help, instead of providing the word. For instance, partner one may say, "Look at the picture for a clue." or "Break the word in half, because you probably know the first chunk."
Coaching or Time is a powerful thing to teach for several reasons. It provides the reader with a small gift of time, which is often enough to try one or two strategies and decode for themselves. It provides their partner with a purposeful and challenging activity. In order to coach well, they really have to think about the word and the strategies they know, in order to decipher which would truly be the most helpful.
We've seen it work with boys and girls as young as kindergarten. So, let the helping continue! Let's just channel it into a way that is truly helpful.
Coaching or Time is also a great strategy to share with parents.