He didn't say that at all. The only fact you can derive from evolution is that some things existed, and now they either do or don't exist. That's exactly what he is saying.

You could argue that maybe some solutions were not even tried before, or that they were tried and abandonned for random reasons. But actually, since the evolution process took a long time, we can reasonably say that we are witnessing the mean outcome of these events. Aka, in this case, the overwhelming majority is a work-related school schedule.

This doesn't invalidate 'free schools' such as Montessori, as these could be good local solutions. They just apparently don't scale to the ensemble of society since they didn't yet and had plenty of time to do so.

Another remark : this doesn't apply to things that were recently invented or discovered.