[by Yago Moreno, original idea from Isabella Wallace]
You will need 4-5 balls of string.
Divide your set in 4-5 groups of 3-4 students.
Make them discuss a topic: the planning of an essay, advantages + disadvantages of something, what do they know about a certain topic.
Every time a student makes a contribution to the group discussion, he needs to be holding the ball of string. Every time someone else wants to say something, s/he needs to grab the ball of string, but the previous student does not let go of the string. At the end of the 5-10 minutes discussion, you will be able to see who has participated and who hasn’t in the discussion.
Even better: if a student is not participating in the debate, s/he will realise s/he is being left out. You will know who has contributed to the discussion, how many times…. And the rest of the students will even put pressure on the free-rider to say something!