From what I've read here on the website and in other postings, I think you can probably just use your one board. The only reason that I would wonder about changing boards would be if your 3 groups were very different--like advanced readers, low readers. If they are heterogeneously grouped, then I think you'll be fine.
If the students have their own menu in their reading folders or in your Conferring Notebook, differences can be noted there, just as we do in any classroom.
