Now, what I love about this method of exit tickets is the self-evaluating the students have to do in placing their sticky note on the stop light. They have to decide how they feel about their level of understanding. And guess what? The students are almost always accurate!! They pretty much "hit the nail on the head" when they take this type of ownership in their learning.
Give each student colored index cards/post-its for their work space. During independent work time or group work, the students use the cards. A teacher I used to work with put red cards on popsicle sticks at the student work centers & prompted them to hold it up when they needed help, rather than calling out. Her classroom was always so quiet!