Yes, my articulation students (r group and s group) made "Our Rocks" and "Silly Stones" in our speech groups. Keep in mind that I work with middle school students! Some days they just crack me up. A couple of years ago I had an 8th grader who loved to write about her pet rock on my white board whenever she would come into the room and I wasn't there. Well, she came back to visit me this year and left the notorious "My Pet Rock Died" picture on my board. So my students asked me about the story and I told them about my Lexi and her Pet Rock. I also told her that Lexi worked on R's so I was fine that she always talked about her pet rock. It gave her plenty of times to practice her sounds. Well that gave me the idea to actually make "Our Rocks" in the R group. As you can imagine, the S Group did not want to be left behind so they made Silly Stones.
You have to make articulation groups fun no matter what age, but in middle school you REALLY have to get creative sometimes and silly! You try saying "Our Rocks"; it takes a lot of concentration even when you DON'T struggle with the R sound!