How to Make a Clash-Free School Timetable: A Step-by-Step Guide
The timetable decides every teacher’s week for a whole year. Here is the order of work that gets you a clash-free version without three weeks of erasing.
Every year, someone in the school (often a senior teacher or the vice principal) spends days with a large sheet of paper, a pencil and an eraser, trying to fit every subject, every teacher and every room into a week without a clash. Then a new teacher joins in July and half of it has to be redone.
There is no magic formula, but there is an order of work that makes the job much faster and the result much more stable. The key idea: place the hardest constraints first and the most flexible periods last.
Step 1: Collect every constraint before you draw a single grid
Most timetable rework comes from a constraint someone forgot. Before you start, get these in writing:
- The school day: start and end time, number of periods, period length, breaks and assembly.
- For each class and section: every subject and how many periods per week it needs.
- For each teacher: subjects and classes they teach, and their maximum periods per day and week.
- Part-time and visiting teachers: the days and hours they are actually available.
- Shared rooms: science labs, computer lab, library, music room, sports ground.
- Fixed slots: assembly, games for the whole school, combined classes, co-curricular periods.
Step 2: Place the fixed and shared periods first
Anything that can only happen at one time, or in one place, goes on the grid before anything else:
- Whole-school slots such as assembly and common games periods.
- Periods taught by part-time or visiting teachers, inside their available hours.
- Lab periods, since several sections compete for the same room. Double periods for practicals go here too.
- Combined periods where two sections are taught together.
Step 3: Place the subjects with the most periods
Mathematics and languages usually have the most periods per week, and many schools prefer them in the morning when students are freshest. Place them next, spreading each subject across the week so a class does not get three maths periods on Monday and none on Tuesday.
Step 4: Fill in the remaining periods, teacher by teacher
Now work through the remaining subjects. At each step, check three things for the teacher you are placing:
- They are not already teaching another section in the same period.
- They do not exceed their maximum periods for that day.
- They are not teaching too many periods in a row without a free period.
Step 5: Balance the load and check for clashes
Once every period is filled, check the timetable from three directions: by class, by teacher and by room. A good timetable looks reasonable from all three. Common fixes at this stage:
| Problem | Typical fix |
|---|---|
| A teacher has 7 periods on one day and 3 on another | Swap a period between days within the same class |
| A class has the same subject twice in a row (unplanned) | Swap with a different subject on another day |
| A lab is double-booked | Move one section’s practical to a free lab slot |
| A teacher has no free period all day | Swap one period with a colleague who has a free slot |
Step 6: Plan for absences before they happen
Every week, some teacher will be on leave. Decide in advance how substitutions are arranged: who is free in each period, how substitute load is shared fairly, and how the substitute teacher is told. Keeping a simple record of substitutions taken by each teacher prevents the same few people covering every absence.
Step 7: Publish it where people will actually see it
A timetable printed on the staff room wall is out of date the first time a period changes. Share each teacher’s own weekly timetable on their phone, and each class timetable with students and parents, so that any change reaches everyone at once.
A short checklist before you finalise
- Every class has the right number of periods for every subject.
- No teacher is in two places at once, and no room is double-booked.
- Visiting teachers are only scheduled inside their available hours.
- Teacher loads are within limits on every single day, not just across the week.
- There is a clear process for substitutions.
TriaCampus includes timetable building, each teacher’s live weekly schedule, and leave requests with substitute arrangement. Browse all features or book a demo.