The best teaching environment for learning is one where a teacher can manipulate time/content to meet the needs of every student. This is best illustrated by lower school homerooms where teachers have blocks of 60 to 180 minutes with students. For private-independent schools, the stakes are high. The expectation is that students will succeed at and above what they and their parents can imagine. This requirement for every student to succeed, implicit in the admitting of mission-appropriate students, must now drive our concept of teaching time in the 21st Century School. The 20th century paradigm for class length was the seven- or eight-period day of 40- to 50-minute classes over a school year of 180 days—yielding 8,100 minutes (180 x 45) of teaching, or 135 hours, per class each year. The justification for this paradigm was compelling. There was an enormous amount of knowledge that students had to learn in order to participate in the industrial society. The architecture of schools emphasized this knowledge acquisition with rows of desks facing the teacher at the front “armed” with chalk and ruler, and working in isolation from colleagues. And the aristocracy of schools ensured that students not only entered a class, but entered their “class” in terms of the type of knowledge presented: abstract and university-bound, or practical and trades-bound.