A game-based classroom response system
As a teacher you should sign-up for free at getkahoot.com to create a quiz, discussion or survey. I found the quizzes very useful as a formative assessment tool. I created quizzes, the students created quizzes and we worked in groups to answer the questions (this was mainly due to the fact that we lacked the technology in the school for each child to have a device).
Kahoot generates a pin number for each quiz, discussion or survey. If students are using a hand-held device (phone, tablet, etc) then they simply download the Kahoot app (which is available for free on all platforms – Android, IOS, etc) and enter the pin. If using a desktop or laptop then students simply open kahoot.it and enter the pin.