The timetable that was redesigned

A school moved its hardest subjects to the morning and its results improved in two of them and fell in a third. The third was physical education.

The reasoning behind the change was sound and partial. Attention and working memory are generally better in the mid-morning for adolescents, and tasks requiring sustained concentration benefit from being placed there. Mathematics and the sciences gained. What the plan did not account for was that physical performance follows a different curve: body temperature, reaction time and muscle strength peak in the late afternoon, and a timetable that fills the morning with demanding academic work must put movement somewhere else.

The second-order effect was larger than the first. With physical education moved to the last period, attendance at it fell, because the last period is where other commitments bite. Across a year the number of active minutes per student dropped by about a fifth, and the school's own data linked active minutes to attendance in all subjects.

The revised timetable kept the morning for concentration and moved physical education to the middle of the day, splitting the long afternoon into two shorter blocks. This was unpopular with staff for reasons of logistics and improved all three measures.

The general lesson is about optimising one variable. A timetable is a system with several constraints that pull in different directions, and a change justified by the strongest single piece of evidence will usually damage something the evidence was not about. The useful question before any such change is not 'what does the research say' but 'what else does this move, and who will notice first'.