Current school times practically guarantee that teenagers will be too tired and sleep-deprived to learn much.
And of course, even I as a pretty severe nightowl learned some things in school. It was just that I was constantly falling asleep and always sleep deprived and had to catch up on sleep every single weekend. I likely would've done much better had school started 2h later.
Not in all cases. But there are absolutely logistical advantages some kids have and others don’t, and some kids suffer significantly for that disadvantage.
Always exceptions to rules of course. And humans can still do impressive things under duress. Maybe the question is not how do they manage, but how much better could they manage under more ideal schedules, and how many more kids would do better as well?