But this study is asserting that the earliest 8am class, of a system that runs 8am to 4pm, has the worst performance.
It can’t say that a 9am class in a system of 9am to 5pm would have better performance at 9am, and it certainly can’t say that the system as a whole would have better performance. Maybe 5pm is too late and affects child care or dinner or night jobs and now students are distracted all over again.
There is way more research than just this study that links early starts to poorer educational performance.
Your speculations have nothing to do with anything in the study, depend on facts that are not supported by any research, and are contradicted by other studies on this topic.
It can’t say that a 9am class in a system of 9am to 5pm would have better performance at 9am, and it certainly can’t say that the system as a whole would have better performance. Maybe 5pm is too late and affects child care or dinner or night jobs and now students are distracted all over again.