In my experience, the videos can be quite shallow, but then the textbook I use for A-level (16-18 year olds) has a very prescriptive approach. I can assist with the understanding, making-links aspect of their learning. I think providing links is fine and probably a good idea. I would expect students to soon realise that attending classes, and particularly extra help, is a much more effective use of their time than sitting through the videos, albeit ones that form part of a great resource.
I do have students that would enjoy learning from KahnKhan Acadamy but these are the ones who spend time watching Vsauce and similar. As they are so motivated, they would be unlikely to replace classes should they be given the choice whether to attend.