Thirdlander replied, "We do, but they keep doing it and they call us liars!"
My next suggestion which admittedly was not well considered was, "Okay, so maybe can other people in our class watch out for this problem and try to help?"
So come to find out when I picked them up from recess, everyone was astir. Turns out the Thirdlanders had linked arms and encircled a few of their pals to protect their game. This caused the rascals to ratchet up their mischief. A near riot ensued. "Now our game is banned!" yelled one Thirdlander. I said, "Well, that's a drag. I probably should have just talked to those little peeps myself. But it does sound kind of cool that you all linked arms and tried to help."
"It was awesome," chirped a chorus of smiling Thirdlanders. I'll try to sort this all out next week. Obviously my class is totally in the right.