Copyright and Fair Use LR

I was debating about number eleven, which states: “A teacher videotapes a rerun of Frontier House, the PBS reality show that profiles three modern families living as homesteaders from the 1880s did. In class, students edit themselves 'into' the frontier and make fun of the spoiled family from California. This is fair use.” The answer turned out to be true because video can be pulled into multimedia projects. I am a little confused on what is allowed and what is against the law when it comes to using video in the classroom because number fifteen says using video compilation as part of a lesson is not covered under fair use laws. I am using video clips for some of my hooks in my lesson plans, but I never would have guessed that the use of these clips may be illegal. I feel as though if a video is being used for educational purposes, then it should be allowed to be used. Since copyright and fair use laws are not that simple, I should probably read through them more closely before I continue planning lessons with video clips.