Now, a lot of skeptics might say, well, hey, this is all great, philosophically, this whole idea of mastery-based learning and its connection to mindset, students taking agency over their learning. It makes a lot of sense, but it seems impractical. To actually do it, every student would be on their own track. It would have to be personalized, you'd have to have private tutors and worksheets for every student. And these aren't new ideas -- there were experiments in Winnetka, Illinois, 100 years ago, where they did mastery-based learning and saw great results, but they said it wouldn't scale because it was logistically difficult. The teacher had to give different worksheets to every student, give on-demand assessments.