I've taken online classes and i did not like them. Me and millions of other people don't learn well that way. You can't force someone to learn in a way thats bad for them. Online classes should be optional but not the norm.
Plus kids need face to face interactions and social skills. Plus they need to physically be tehre for some lessons to handle materials.
There is a lot more to Education than just learning facts. You can signup to an online course... And it will help you know some facts, give some exposure working in virtual groups... And that's it. But a 'real' classroom gives you much more than just that. You will experience human face to face interactions and the real feeling of working in a group. Most of our professional career, even though we get promoted for our individual performances, we need to interact with people, with groups, and our success almost always measured by how successful we did as a group... And how much we were able to influence the group to be successful. It's impossible to get this 'knowledge' without working with real people & in real groups.