OK, let me state it thusly:
I am a night owl, and especially as a teen I was. However, our start times were 8.50am... I remember trying to wake at 5am to run for a while and I could not adjust my night routine no matter how I tried (felt like shit all day, dozy and took way less info in). 7am ish awakening meant anywhere from 6-8 hours was possible and enough (I lived 5 - 10 mins from school).
It pisses me off no end that melatonin as a supplement has been banned OTC here. No fuck ing reason except maybe to protect sales of ambien. Totally unfounded.
As for distractions, come on - they have to be a big part now, esp given the blue light of screens and LED lighting. That is completely contrary to sleeping seeing light that imitates daylight.
Take into consideration that many high school students in major cities take the bus and train to school. So, if you start at 7:35am, you have to be up by 5:00am. And if you go to bed between 11-12, thats 5-6 hours of sleep, assuming you sleep through the WHOLE night--many people do not. For many students, there schools are not across the street. I had to take a 15 minute bus ride to school on the NYC bus, and that was considered close.
Yes, artificial light is distracting, no doubt about that. However, a 7:35 start time is too early. Again, youre not taken into consideration getting up, brushing teeth, eating breakfast, then driving or taking transportation to school. Some of these kids then have to be up at 5:00am, perhaps earlier. Its okay if school starts at 7:30am and you live right across the street. For many, that is not the case.