We had friends who who pulled their kid out of school and found the same thing.
He was out for surgery and they gave him several weeks worth of school work.
He went into his room and came out about 2 hours later and had it ALL done.
She was absolutely blown away, and that’s when they realized what was going on in public schools and they yanked him for a few years. he eventually wanted to go back but by then he had at least gotten a decent education.
As a high school sophomore, I made the decision to leave the band and transfer into a chemistry class. Everyone else was a junior or senior. My dad recommended that I do some "catch up" to account for switching 9 weeks into the year. I settled in with the text, read every chapter, did every exercise. All done in 3 1/2 weeks. Easy A in the class and good prep for UCSD.