List constraints before drawing grids
Write down teacher availability, room capacity, double periods, laboratory access and shared staff before opening the timetable. Most clashes come from constraints that were never written down, not from scheduling software.
Build the core first, then fill
Place the subjects with the hardest constraints — sciences, languages taught by a single teacher, shared halls — then fill the flexible periods around them. The reverse order is what produces week-eight collapses.
Protect teaching time from administration
Assemblies, clubs, sports and staff meetings should have fixed slots. When they float, they land on lessons and the timetable quietly becomes fiction.
Publish one version and date it
When the timetable changes, publish a numbered version with a date so staff know which one is current. A change log is cheaper than a group chat arguing about the Monday schedule.
Review in week two, not week eight
Check what actually happened against the plan after the first full cycle. Small corrections early cost far less than rebuilding the timetable mid-term.