It has been proven that the brain is not fully capable of learning until around 10am, so our whole first lesson is completely pointless. On top of this, teenagers' body clocks are naturally different. People say that they go to bed late and wake up in the middle of the day, but we can't help it! It's our natural cycle to sleep at those times. They actually tested this with one school. Classes started at 10 or 11 and their grades were much higher than average.
And really, who wants to get up at 7 in the morning?
One, is starting school in August (like in Switzerland).
Two, is starting school early in the morning, like at 7:45.
Especially in a country like Switzerland (and Western Europe in general) where sunny days are not many and summer is rather short, it seems to me more reasonable to let people in general and teenagers in particular take as much advantage of summer as possible.
As for starting early in the morning, we could probably say that people differ in that, but I think it has probably been set so for the convenience of parents, so they send their kids to school before they go to work.
It would be interesting to give an (experimental) option to students to start earlier or later and see what the majority would do. I have not met one single student who particularly enjoyed starting school early, but I have met students who did not mind.
I think the starting and ending time is just one issue. The whole school system is out-dated and does not take into account life evolution and does not adapt to it or evolve with it.
we could sleep do homework and play as long as we wanted