How I Use It
I have used Kahoot as a review activity in my classroom when preparing for a summative assessment- like identifying parts of speech, literary terms, or the difference between a simile and metaphor. It works really great for just that...review. It could also be used as a an anticipatory set...you could set up a little quiz to get students thinking about a new topic, or to see what they already know about the topic. Because the tool was so engaging for students (my middle school students LOVE the competitive nature) I even let them "choose" from some of the already-made quizzes during free time to play around with. Be careful with this! Anyone can make their quiz "public," so it's easy to run into false information or just plain bad spelling errors. Teachers should preview the quizzes first.
Overall a great tool to use for formative assessment, whether it is a review in class, or even to begin a unit to get students thinking. You won't hit super high cognitive thinking here- really just recall-type questions (all multiple choice). I did start creating a couple students accounts as a way to involve my students on a little deeper basis- if THEY create some of the content and quizzes for each other, it requires them to think about the content a bit more.