I'm in the US.
Most of my jobs have started at 9 am and ended at 5 pm, which is fairly standard. Usually, there's half an hour for lunch, but I did work one place where they gave us a paid hour for lunch, which was unusual.
While 9-5 is a standard, there are places that are 8-4, or 8:30-4:30. Where my sister works, they get an unpaid hour for lunch and their work day is 9-6 to accommodate that. There are all sorts of variations on the "standard" schedule. And this is only for office jobs. Factories and hospitals and retail stores and other places that are open longer hours every day have a variety of different shifts.
If you are salaried, while your standard work hours may be 9-5 or some variation of that, you are expected to work until your job is done, which is why so many people get to work early and stay late--they have work that must be finished by a certain time and they need to do it.
Many companies offer flex-time, where all employees need to be in the building during a certain core number of hours, say 10-2, but as long as you work an 8 hour day, you can come in as early or late as you like, as long as you are there during the core hours.
Add in that the average commute in the US is 45 minutes one way, and you can see why people are up and eating breakfast at an early hour.
As for schools, for a good part of the year it's either send the kids to school in the dark or have them come home in the dark. A surprising amount of the scheduling is due to the buses. Most school systems have one set of buses. They send them out early for the high school students, then do a second round for the middle school/junior high students, and then a final round for the elementary school kids. They don't want the drivers waiting around, as they are paid by the hour.
There are a great many places in the US where the kids cannot walk to school due to distance and lack of sidewalks/street lights/other safety issues and where there is absolutely no public transportation.
High schools start early and get out early in part so that the students can have part-time after-school jobs, and to allow time for all the extra-curricular activities, such as sports and band. If school gets out too late, the sports teams would be practicing in the dark.
Another factor in starting school early is that parents are leaving for work early. They don't want to leave small children home alone, trusting them to remember when to go out to catch the school bus. The parents would either have to drive the kids to school on the way to work (and the school might not yet be open) or pay someone to mind the children until the school bus comes.