How to build a school timetable without clashes: a step-by-step method

Step 1: collect every constraint before you start

Most timetable problems are discovered after the timetable is published. Collect the information first, in one place:

• Periods per week for each subject in each grade
• Which teacher teaches which subject to which section
• Teachers who are part-time or unavailable on certain days
• Rooms that are limited: labs, workshops, sports hall, computer rooms
• Subjects that need double periods, such as practical sessions
• Shifts, breaks and the start and end time of the day

Step 2: place the hardest periods first

Start with what has the fewest options. Practical sessions that need a specific workshop, part-time teachers, and double periods go first. Subjects with many available teachers and rooms go last. If you do it the other way round, the last pieces will not fit.

Step 3: fill section by section, and check teachers as you go

Work through one section at a time. After each period you place, check that the teacher is not already teaching another section at the same time. Doing this by eye on a spreadsheet is where most clashes come from, so use a tool that blocks a teacher from being booked twice.

Step 4: review from the teacher’s point of view

A timetable can be correct for every class and still be unfair to teachers. Print each teacher’s week and look for days with too many periods in a row, long gaps, or one teacher with all the last periods.

Step 5: publish once, then change carefully

Share the timetable with teachers, students and parents from the same system you used to build it, so everyone sees the same version. When something changes, update it there instead of sending a new file.