Khan Academy has a Coaching feature that allows students to practice a new skill and receive immediate feedback. You can also track student progress. Now the classroom can be used for valuable discussions like how specific skills can be applied in their real world (relevanancy). Or to allow peer to peer teaching, small group instruction, and one on one instruction when all else fails.
"A new study from the Stanford Graduate School of Education flips upside down the notion that students learn best by first independently reading texts or watching online videos before coming to class to engage in hands-on projects. Studying a particular lesson, the Stanford researchers showed that when the order was reversed, students' performances improved substantially."