Why would elementary school start so early?

My daughter’s elementary school starts at 7:20 and they can only arrive from 7:20 until 7:40. At 7:40 the doors lock automatically.

To be there about 7:30, with only a 10 minute drive, I have to get her and my two-year-old up by 6:30 in the morning. That seems really early for five-year-old kids. Am I just used to being a late riser? Is this normal?

It doesn’t seem like the day is balanced and there’s some quirk that makes it all work out to justify the early start. They eat lunch at 10:45 and are done for the day at 2:45. I can’t imagine this fits anyone’s working schedule or makes anyone’s life easier. I don’t see any way this benefits the kids, or even the teachers. It would seem someone with the district must know that, right?

The only upside I see is they must be able to use one set of buses and bus the elementary kids in first, then middle school, then high school. That doesn’t seem like enough to warrant an entire generation of sleep deprived kids, but again, I feel like I’m missing something.

Can anyone explain this to me? What am I missing?