Constraint recipe
Availability has two levels. An **unavailable** period means the teacher must not be scheduled then, for example childcare, another campus, or a fixed part-time day. A **preferred free** period means they would rather not teach then, but could if needed. Mark true blockers as hard rules. Team-taught lessons need every teacher free in the same period.
Key takeaways
- Unavailable means must not teach; preferred free means would rather not.
- Part-time non-working days are unavailable, not preferences.
- Team teaching needs overlapping free time for every teacher.
- Relax preferences before you weaken true unavailability.
Why the two levels get confused
A request to avoid Friday afternoon is not the same as a day the teacher does not work. Treating every request as mandatory quickly makes the timetable impossible, especially for shared specialists and part-time staff.
Write down the reason for each window: contract, campus travel, childcare, or preference. That reason tells you whether the window should block placement or merely discourage it.
Shared lessons need shared availability
Each teacher on a team-taught class must be free in the same period. Checking calendars one teacher at a time misses the real bottleneck: the overlap window for the whole team.
See teacher availability constraints for the full classification and examples.
What to do next
- List every availability note for each teacher with the reason behind it.
- Mark must-not-teach windows as unavailable periods.
- Mark would-rather-avoid windows as preferences unless policy requires otherwise.
- For shared lessons, draw the overlap of all required teachers' available periods.
- Count whether required lessons fit inside those overlaps.
- Relax preferences before you change true unavailable periods.
Common mistakes
- Coding every teacher request as unavailable
- Checking team members separately instead of their common free periods
- Adding availability after pinning lessons, which can make pinned slots illegal
Quick answers
Is teacher unavailability always hard?
If the teacher truly cannot teach in that period, yes. A preference to avoid a period should usually stay soft.
Why can one part-time teacher affect many classes?
Every lesson needing that teacher must fit their working days and periods. Shared lessons also need the other teachers and the class free at the same time.