California’s new law bans schools from starting before 8am

You have to understand that not everyone does well in the morning. It's completely unfair to expect everyone to get up and be functioning at the same level in the early morning. That's going to advantage some, and disadvantage others. That's what this is about.

Nothing stops the early bird from getting up early and doing all the things you ascribe to.

Also, later school start times have in other states led to better academic performance, better behavior, etc., independent of any control for bedtime.

This decision has no downside. It's like mandating that hot dog vendors not sell disguised dog turds.

Starting an hour layer improves SAT scores:

One of the first test cases happened in the township of Edina, Minnesota. Here, school start times for teenagers were shifted from 7:25 a.m. to 8:30 a.m. More striking than the forty-three minutes of extra sleep that these teens reported getting was the change in academic performance, indexed using a standardized measure called the Scholastic Assessment Test, or SAT.

In the year before this time change, the average verbal SAT scores of the top-performing students was a very respectable 605. The following year, after switching to an 8:30 a.m. start time, that score rose to an average 761 for the same top-tier bracket of students. Math SAT scores also improved, increasing from an average of 683 in the year prior to the time change, to 739 in the year after. Add this all up, and you see that investing in delaying school start times—allowing students more sleep and better alignment with their unchangeable biological rhythms—returned a net SAT profit of 212 points. That improvement will change which tier of university those teenagers go to, potentially altering their subsequent life trajectories as a consequence.

(This is one example, that has been replicated many times, he covers more in the book.)

It saves even saves lives:

Yet something even more profound has happened in this ongoing story of later school start times—something that researchers did not anticipate: the life expectancy of students increased. The leading cause of death among teenagers is road traffic accidents, and in this regard, even the slightest dose of insufficient sleep can have marked consequences, as we have discussed. When the Mahtomedi School District of Minnesota pushed their school start time from 7:30 to 8:00 a.m., there was a 60 percent reduction in traffic accidents in drivers sixteen to eighteen years of age. Teton County in Wyoming enacted an even more dramatic change in school start time, shifting from a 7:35 a.m. bell to a far more biologically reasonable one of 8:55 a.m. The result was astonishing—a 70 percent reduction in traffic accidents in sixteen- to eighteen-year-old drivers.

To place that in context, the advent of anti-lock brake technology (ABS)—which prevents the wheels of a car from seizing up under hard braking, allowing the driver to still maneuver the vehicle—reduced accident rates by around 20 to 25 percent. It was deemed a revolution. Here is a simple biological factor—sufficient sleep—that will drop accident rates by more than double that amount in our teens.

There's more reasons, like improving attendance and decreasing drug/alcohol use, but these are the ones that stuck out to me. There was another statistic that I can't immediately find a quotation for that was pretty mind-blowing for me, which was that in university, the difference in performance in controls and students who started class an hour later was equivalent to the difference between controls and students who had a professor a standard deviation above the average. They even showed that this was dose dependent (an extra hour later had more effect). I think it's pretty incredible, considering the skill gap between an average professor and a great one, that simply taking a class at a 10am instead of 8am can increase learning so much.

[1] https://www.amazon.com/Why-We-Sleep-Unlocking-Dreams/dp/1501...