A site like Khan academy really is helping teachers take a flipped approach to learning. While there is a lot of great content out there on the web, it is important that teachers don't just send their students to links. It must be relevant and tailored to the needs of the class. I find that teachers like myself are actually creating videos for the lessons that are specific for their students and posting them online on a class site. This becomes a resource site that students can then rely on throughout their entire unit/year and refer back to it when necessary.
The idea of flipped learning is for students to watch the videos at home so they have an understanding of the content when they enter the classroom and then inside the class the knowledge is pushed further through application, experience and discussion. It also depends on your students though and their available technology at home. For a private school, this likely will be a system of learning that could be easily used. However, if students are from less fortunate public schools, they likely will not have access to the technology at home to do this pre-learning.