It really shows that you know nothing about sleep-related disabilities. I know someone suffering from idiopathic hypersomnia[1]. You can't just "choose" to go to bed earlier to wake up earlier in the morning. Sometimes it might work, most of the time it doesn't.

You think it's the disabled person's responsibility to never put a burden on others when others' expectations puts an unreasonable amount of burdens.

And we're talking about this specific kind of disability, but as someone else said in a sibling comment, it could be anything. Imagine you really have to go to the bathroom for some reason (pregnancy, diarrhea, ...). That can happen to a lot of people. Should all of them be prevented from being accepted into class ?

That's why we speak about "empathy, tolerance, flexibility". Empathy towards the weaker few, not empathy towards the "normal" many.

[1]: https://www.mayoclinic.org/diseases-conditions/hypersomnia/s...