I think much of what Mr. Bernstein advocates already happens in an informal way in many high schools. But the numbers are not large for a variety of reasons: college requirements, year-long courses, participation in school sports, and the wish to participate in second semester senior activities, to name a few.
But, for me, the real show stopper to Mr. Bernstein’s suggestions was his casual comment at the end that this was a “win-win-win!” since the money saved could be used in a variety of ways.
If the students skip the whole senior year then, yes, money would be saved, as fewer staff could be hired. But if a significant number of twelfth graders leave at the end of the first semester, the school is in the position of either firing the teachers and staff needed for these students, and then rehiring them the following year, or allowing everyone to have smaller classes for a semester.
Allowing the smaller classes would save no money at all. Firing and then rehiring is brutal, and would leave high school teachers with the same lousy security and pay that so many itinerant college teachers now deal with. I would hate to see that happen.