In-person classes, sports classes, and music classes should not require active supervision for the duration of the class. Online classes might require a bit, to make sure they are not goofing off.
However, unless your kid is blessed in the executive function, motivation, and responsibility departments, you will probably have to remind them to get going in the morning, log in to their classes, stay on top of their homework, and study for exams. Basically, function as their executive assistant slash tutor. Add driving, cooking, and cleaning to the mix, and it can easily be a full-time (unpaid) occupation.
My kid is upper elementary and doing about 20 hours of home-based education per week. I expect this to be bumped up to around 40 hours in middle school. I really hope that my kid will be able to manage all of homeschooling stuff independently in a couple of years, but I'm not holding my breath.