I have always liked the idea of a flipped classroom, especially as a former high school math teacher. I ran with the flipped classroom my final 2 years in the classroom, but when students watched their lessons I had no way of knowing who was prepared coming into class. EdPuzzle can help with this. EdPuzzle takes videos from sites such as YouTube, National Geographic, TedTalks, and many others or you can upload your own video. This last feature is really cool as YouTube is blocked for most student access. EdPuzzle allows you to break up a video and ask questions through key parts of the lesson to check for understanding. It also allows you to crop the video so that you are only showing the part of the video you need. Students are also given the option to re-watch that section of the video if they need to. The teacher can then check on their understanding of the topic by viewing the results and see how many times the student re-watched it or if they saw the whole video. Below is an example. Oh, did I also mention that this is free!