Teacher constraints in a timetable: how to collect and approve them

The short answer: you collect the constraints in writing, from each teacher separately, before you start placing lessons. You phrase each constraint as a clear rule (who, when, what), mark whether it is mandatory or a wish, and approve them one by one. What was not approved does not enter the system. That way you know exactly what the system is built on, and what you can answer a teacher who asks why her request was not kept.

Most of the pain of a timetable is not in the placement itself, but in the constraints: notes, WhatsApp messages, "I told you in the corridor". This guide puts this stage in order. The full picture, from setting up the school to publishing, is in the complete guide to building a timetable.

Common kinds of constraints

Almost everything teachers ask for falls into one of these groups:

A day off for a teacher is really a "Not available" constraint on a whole day. Who is entitled to such a day and on what terms is a decision of the school management, according to the rules and agreements that apply to it. The system does not decide this. It only needs to know what was decided.

Mandatory vs wish: what really has to hold

This is the most important decision in the constraints stage. If every request is mandatory, very quickly there is no possible timetable.

• Mandatory - something that must not be broken. A teacher who works somewhere else on Wednesdays. One sports hall. A teacher who teaches part-time and has a ceiling on hours.
• Wish - something you try to respect. "I would rather finish early", "I prefer not to start in the first period".

A rule of thumb: a mandatory one is something that if it is not kept, the teacher simply will not be there, or the lesson cannot take place. Everything else is a wish. It is worth saying this to the teachers already in the request, so that they do not write "mandatory" on everything.

Collect from teachers by link, not a paper form

A paper form looks simple, but it creates double work: someone has to type it, decipher handwriting and chase whoever did not return it. It is better for each teacher to write for herself, and for the answer to arrive straight in one place.

This is how it works in Teaching School:

1. In the "Teachers" screen you tick the teachers and press "Send constraint request". Before the first send you need to confirm the school's email address, so that the messages are sent in its name.
2. Each teacher receives an email with a personal link. There is no password. She opens it on the phone or the computer and goes straight to the form.
3. The form has a free field "In your own words" (for example: "I cannot on Tuesdays, and I would rather finish by period 6"), and also a quick tick for days when she is not available and for the maximum periods a day.
4. The teacher sees what she submitted and the state of each constraint: "Waiting for approval", "Approved" or "Not accepted". She can go back to the link and add.

The email itself cannot be replied to. The answer is delivered only through the link, so no constraint gets lost in a mailbox.

The timetabler has a table of the requests: to whom it was sent, who opened the link and who answered. That way you see exactly whom to remind. A request cannot be sent to a teacher without an email address, and the system says so before sending.

Wording for the request, to copy

Even when the request goes out by email, it is worth sending the staff a short message that explains what is being asked. Sample wording:

Hello everyone, we are starting to build the timetable. Each of you will receive an email with a personal link for submitting constraints. Write only what really matters: days or hours when you cannot teach, and mark what is mandatory and what is desirable. A constraint marked as mandatory needs a real reason. Deadline: Thursday. After that we will build the timetable according to what was submitted.

Common mistakes in collecting

• Not giving a deadline. Then constraints keep arriving even after the timetable has already been built.
• Accepting "I would rather not" as mandatory. Every wish that becomes mandatory narrows everyone's options.
• Forgetting constraints of the whole school. Shared rooms, short days, hours of teachers who also teach at another school.
• Approving without reading. Always compare what was written with what the system understood.

Free writing and the timetabler's approval

The timetabler can also write constraints herself, in the same free language: "Ronit cannot on Tuesday". This is convenient when a teacher said something orally, or for constraints of the whole school and of classes.

Every constraint, from both sources, is shown in the constraints screen in three layers:

• What was written - the original text, as submitted. It is always kept.
• What the system understood - the structured rule: kind, who, days, periods, mandatory or wish.
• Approval, fix or rejection - the timetabler's decision.

No constraint enters the calculation without approval. A constraint that is waiting does not affect the timetable.

It is important to know what happens behind the scenes: the free text is interpreted by a language model. When the system does not understand a sentence, it is marked "Not understood", and it cannot be approved as it is. You fix it in a simple editor (the kind of constraint, days, periods, and the "mandatory" tick) and save. In practice, the shorter and clearer the sentence, the more accurate the interpretation. "Danny not on Thursdays after period 4" is better than a paragraph of explanations.

One more thing: if you later change the school week (for example you remove a day or a period), constraints that no longer fit return for checking with an explanation of what changed.

When constraints contradict: understanding what collides

Sometimes there is no timetable that meets all the mandatory ones. A made-up example: Ronit is the only math teacher in the grade, she is not available on Tuesdays, and at the same time it was set that math in this grade must be every day. The two rules cannot hold together.

In Teaching School, when a timetable cannot be built, you get the smallest group of rules that contradict each other, with an explanation in plain words. It is enough to release or change one of them to try again. A lesson that was locked by hand or a ceiling of hours a day for a teacher can also be part of the contradiction, and they appear in the list by name.

When there is a timetable, the "What was met and what was not" screen shows every approved constraint: met or not, and the reason. This is what you answer a teacher who asks why her wish was not met.

If some of the constraints arrive in the middle of the year, there is a guide to changing a timetable in the middle of the year. And if you are still choosing a tool, here are 8 questions before you choose timetable software.

Written by the Teaching team · Updated on 14 October 2026.