Labs help students learn
I read the articles about flipped teaching with great interest. I believe a good solution would include having labs (like those for chemistry, physics, biology, etc.) for many courses that now do not have labs. Labs would provide hands-on experience in addition to eyes-in-books reading experience and eyes-on-the-screen video experiences.
I do believe online learning is a good adjunct to the traditional classroom, but not a complete replacement.
I spent the first two years after graduating from Harpur teaching high school math and chemistry (in New York state; all Regents classes). I taught elementary algebra, plane geometry, intermediate algebra, trig, advanced algebra, solid geometry and chemistry. Thinking back on that experience I realize the chemistry lab gave my chemistry students some very valuable pluses. Something similar was lacking in the math courses. I wish I had recognized it then; I probably would have tried some math labs.