As someone who’s direct family member manages a school schedule in the US, it’s sports. Schools are not for academia anymore. Everyone wants little Timmy to grow up and be a famous American Football star and get that scholarship. You have to start school early enough that it ends early afternoon. Which then allows for after school sport practice which finishes around the time mommy and daddy finish their 9 to 5. Then the games are scheduled after that so the parents can come watch and spend money. The spend money is a big one as they are wasting millions on these arenas for sports while the science labs have textbooks with no spines left.