Each family sets up a program to fit their needs.
As one example, each child has an assignment appropriate to age and grade level. They can do their work individually, or sometimes the older kids can tutor the younger ones. Sometimes they work in one room, or sometimes separate rooms. Sometimes they work individually at the computer, or do independent research at the library. There are many different ways to set up a program. I know many home school families, and each one had a system that fit the specific needs of that family.
In early America, the one-room school house for all grade levels was common.
In the 1920-30s, My dad attended a one-room rural school house through high school. One teacher for all the kids, every age, every grade. After graduation, he worked for the Navy as a civilian, installing special equipment in submarines. When WWII started, he enlisted in the Navy. Because he had a rare technical skill that the Navy needed, he enlisted as an E-4 (not E-1), was issued his uniform, and reported for duty. He was not even sent to boot camp. At the end of the war, he was an E-6. The Navy offered him an officer commission as Ltjg if he wanted to stay in, but he declined. Instead, he went to college and got his four-year degree in two years, in electrical engineering (his name is posted in that engineering college's "Hall of Fame"). He worked for Bell Labs (and has patents for his inventions), Lockheed, NASA, and various Navy departments.
I only say all that to show that a student can get an excellant education even in one humble room with kids of all ages mixed together. The students were poor and barefooted in overalls. No computers or high tech equipment. Only one teacher. But they were taught the fundamentals of their subjects, and they were taught how to study and be self-disciplined. After that, they could learn any subject they took up in college.
My dad was not a special exception. Many, many of our country's best scientists, doctors, writers, entrepreneurs, etc., came from that same kind of background. Many of my friends home schooled their children, and the children went on to college, military, or successful jobs, same as other kids do.
It depends on the situation. I can't give an example for each family. But even government school teachers get pregnant or sick. They can get subs, and home school parents can get subs too.
Parents don't teach their children "ALL THE DAY". A home school day doesn't require as many hours per day as a government school. The mom isn't sitting for six hours a day in a room with the kids. Home schoolers don't need time for commuting to school, no car-pooling, taking attendance, getting the lunch orders, handing out papers, sending notes home to parents, parent/teacher conferences, etc. While the kids are doing their assignments, mom can throw the laundry in the washer, make phone calls, cook supper, etc. She is still there to answer questions, but she can also do other things at the same time. No big deal.
That's fine. I said, home schooling is not for everyone. If you don't want to home school, no one will force you. If you are satisfied with your kids' school, then that is great. I am not trying to persuade you to home school, no way. I am just saying that if other families want to home school, they should be allowed. I don't want anyone to force you to home school, and I don't want anyone to force other families to use government schools. I think that is fair.