How to Change a School Timetable Without Creating Clashes

The timetable is published and term has started. In the second week of October a teacher leaves, and the replacement can't come on Tuesdays. Moving one lesson to another period looks like enough. But if the class has another lesson then, the teacher another class, or the lab another group, one move sets off a chain of clashes.

A timetable is never done once. So what really matters is being able to change it without breaking it.

Drag and drop: Atlas checks before it saves

In Atlas you can drag a lesson and drop it on another period. Drop it onto an empty period and it moves; onto a full one and the two lessons swap. The change is saved instantly, but checked first: teacher, class and room clashes, closed periods, and every required rule in the timetable.

If the change breaks a rule, Atlas doesn't save it and says why, for example: “The teacher already has a lesson at that time.” Only problems your change creates are blocked; a move is not refused because of something that was already in the timetable.

When the lesson won't fit: three options

Sometimes a lesson can't go straight to the period you want. Atlas then says “The lesson cannot move here right now” and offers three options:

1. Rearrange around it: Atlas rearranges a few nearby lessons right away to free the slot. You see a preview first; it is applied if you confirm.
2. Place it here when optimizing: your wish is saved as a strong preference; the next time the timetable is optimised, Atlas tries to put the lesson there.
3. Lock it here (hard rule): the lesson is locked to that period. A lock is a hard rule.

Moving is not the same as locking

A lesson you moved by hand tries to stay put when the timetable is optimised again, but it isn't guaranteed. If a lesson must stay in that period, Lock it; a locked lesson stays there through every re-optimisation. To lock while dragging, set On drag to Lock (hard rule).

Re-optimising with the fewest changes

After several changes you may want to tidy the timetable up. Optimize doesn't start from scratch; it starts from the current timetable. It tries not to move the lessons Atlas placed, protects the ones you moved by hand even more strongly, and never moves locked lessons. You see how many lessons changed, and Undo takes you back exactly to where you were.

To see a completely different alternative without touching the current timetable, use Create new alternative.

Versions: keep every state, compare them

• Save as version the state you like. A saved version never changes.
• Continue from this to carry on working from a version.
• Publish the version the school will use. Only one version is published at a time.
• Put two versions side by side with Compare. The Version Comparison report shows which lessons moved, whether locks were kept, and the difference in the preference report.

A good habit for mid-term changes: save the current state as a version first, then make the change. If something goes wrong, go back to the saved version.

Sharing after a change

Once the new version is published you can email it to teachers. On the duty side, Check Duties shows the duties that no longer fit the new timetable. Sharing is covered in master timetables and teacher schedules.

How the timetable is built in the first place is in the step-by-step guide.