Teenagers in Norwich used to catch a bus at half past seven, an hour most of them spent asleep with their foreheads against the window. When one secondary school moved its first lesson to nine o'clock, the change sounded minor. The results were not. Sleep researchers had long argued that adolescent body clocks shift later by an hour or more during the teenage years. In the first term, lateness fell sharply and morning lessons, teachers said, became discussable: pupils asked questions instead of copying from the board. A follow-up study recorded about twenty minutes of extra sleep per night — modest, but enough to matter for growing brains. Neighbouring schools have watched the experiment closely, and two plan to copy it next autumn if the transport questions can be settled early enough. Opposition came from practical corners. Bus companies would need new timetables, parents worried about later finish times, and after-school clubs and part-time jobs would shrink. A later start, one councillor warned, simply moves the traffic jam an hour down the road. The stakes, everyone concedes, are modest compared with the curriculum debates that dominate education headlines, which may be exactly why the change worked. The school's reply is that timetables serve children, not the other way round. Adolescents' body clocks genuinely run late, the head argued, and forcing teenagers to fight their own biology every morning is a policy choice — one that can be unchosen. What changed, in the end, was less the clock than the willingness to question the clock.
选词填空：______' body clocks genuinely run late, the head argued, and forcing teenagers to fight their own biology every morning is a policy choice — one that can be unchosen.