If you're self-pacing then you don't have to waste time covering material you've already mastered or banging your head against material you're not ready for yet

If you're self-pacing then you don't have to waste time covering material you've already mastered or banging your head against material you're not ready for yet because you're missing fundamentals. If you're much ahead of or behind average then that can be a ton of time—most of your day, even—lost to waste there. Not productively repeating material to attain mastery, I mean, but stuff like taking four weeks to cover a math concept or technique that you could easily have completely understood and internalized in the first week, then moved on to using it in more complex work, if it'd all been presented to you that quickly. Probably 10% of the school day's moving around or preparing to move around or settling down from having moved around, or recess or otherwise not-learning (not to shit on recess—I wish they'd give kids more time for it in lower grades). Another 10-15% is stuff you might not consider part of your "school day" if you're homeschooling (PE, music, library visits, "specials") or nonsense you don't have to worry about (assemblies). So there's maybe a quarter of the day accounted for with no allowances for faster and/or better-tuned pacing or more personalized instruction—poof, 90ish minutes of your day back, 180ish days a year, for 13 years, like magic. Self-pacing you fit it all that remains in 2 or 2.5 hrs, don't need more than minimal breaks so there's minimal padding to that time, and the rest of the day's yours. Public school's alarmingly wasteful of children's time, but saves parents a ton of time, collectively, in exchange.