27 September 2026

Finding Timetable Clashes and Planning Substitutes

A timetable clash is one teacher in two classes at once, or one class with two lessons at once. Both are easy to miss in a spreadsheet and obvious in a list sorted by day, period and teacher. Check for them, compare scheduled periods with what each subject needs, and keep a substitute rule that everyone can see.

Three checks before term starts

• Teacher clashes: the same teacher in two different classes in the same period.
• Class double bookings: one class with two subjects or teachers in the same period.
• Unavailability: a teacher scheduled in a period they are not available, such as a part-time teacher’s day off.

Then compare the periods scheduled for each class and subject with the weekly periods it needs. A subject that is two periods short every week loses a month of teaching by the end of the year.

Workload balance you can see

Count each teacher’s periods per week and the most in any one day. A teacher far above the average, or with six periods in a row, is where fatigue and complaints start. Show the counts rather than a single score, so the timetable in-charge can see the reason behind every flag.

A substitute rule that feels fair

When a teacher is absent, choose only from teachers who are free in that period and not unavailable. Prefer the same subject, then whoever has the lightest day. Writing the rule down, and applying it the same way each morning, stops the same willing teachers covering every gap. The free Timetable Clash Checker applies exactly these checks and suggests substitutes, and the Teacher Workload Planner adds preparation and correction hours to the picture.