When Aaron Sams and I first started flipping our classes in 2007, we made a lot of mistakes, John Bergmann blogs. If you are considering flipping your classroom this fall (or just flipping a few lessons), I want to share with you some of the mistakes we made or have seen others make, so that you don’t have to repeat them. Keep your videos short: Short-short-short! We took our standard lecture and made videos. These videos contained multiple objectives and pieces of content and were way too long. Instead make one video per discrete objective. My rule of thumb is one to one and a half minutes per grade level…