To make it work you need to prepare a set of YELLOW and RED cards.
You set up the activity by explaining the rules:
- if a student talks, interrupts, refuses to engage in an activity etc, s/he will be given the first YELLOW card
- s/he will be given one more chance but in case s/he continues to misbehave, another YELLOW card will be given
- if the situation continues, a student is given a RED card
- a RED card means extra homework, detention, a talk with the principal etc.
A problem that might occur while you try the activity out is the students themselves. They will most probably start writing on the cards or damaging them in some way. In such a case, a good solution might be using colored chalk. Instead of giving the cards to naughty students, mark their desks with red and yellow chalk and you will get a very similar effect. It will also save you time on preparation of the cards.