Public school is not optimized for learning, it's optimized for filling time with nonsense.
If you care about your child's success, teach them how to do math. If they don't know how to read, teach them how to read as well. Probably 2-4 hours of instruction per day, at the absolute max end of the spectrum. Kids from the age of 8+ should be able to accomplish tasks with much less instruction time, and the bulk of the time will be individual effort. Of course, it's mundane and isolating, so don't expect them to sit for hours on end doing school work either.
Public school is what you get when you have one instructor per 20 kids with wildly different backgrounds, parent support and aptitudes. You need 10x better teachers with 1/20 of the load and much more involved parents. If you get all that, and certainly technology is the only way to get it at scale, then yes, kids can be done with academics in a small fraction of their day. They should be spending the bulk of their time in play and exploration.
If you care about your child's success, teach them how to do math. If they don't know how to read, teach them how to read as well. Probably 2-4 hours of instruction per day, at the absolute max end of the spectrum. Kids from the age of 8+ should be able to accomplish tasks with much less instruction time, and the bulk of the time will be individual effort. Of course, it's mundane and isolating, so don't expect them to sit for hours on end doing school work either.