12. Masterfully said. The first day of school, we know when the last day is going to be.
We know that each class is going to be 49 minutes long, 5 days per week, for 36 weeks, less two weeks for semester exams, less two weeks for semester dead week, less two weeks for state-mandated testing. So 150 days or 7350 minutes or 122.5 days, less attendance, morning announcements, early release for pep rallies, guest speakers from colleges and the military, less fire drills, less disaster drills, less textbook issuance, less textbook pickup, less sick leave days or family emergency days.
There IS no "more" time for differentiation, reteaching, and no facility to accommodate acceleration (it's really just one classroom with 32 desks in it, one teacher, and three computers).
The other idea of 100% mastery is that EVERY DETAIL in the course has been studied, analyzed, weighted, and found to be of critical importance to being able to exhibit mastery of that particular detail.
It also denies that there are alternate methods for doing things, or that the skills involved will be relevant at all in the near future (anybody else take sliderule class in high school in 1971 and find Wang calculators in a lab upon arrival at college?)
The one invaluable skill is critical thinking and problem-solving, along with the desire to use that skill. Unless you really think that I need to know the names of all 50 state capitals without looking them up.