Constraint recipe
Spread means distributing a subject's weekly lessons across several days instead of clustering them. Three maths lessons on Tuesday is clustered; one each on Monday, Wednesday, and Friday is spread. Schools usually treat spread as a preference, not a must-have rule. Check double periods, labs, and part-time teachers before you tighten spread.
Key takeaways
- Spread is about which days a subject uses, not how many lessons it has.
- Double periods and workshop blocks may intentionally cluster lessons.
- Part-time teachers and scarce rooms can make even spread impossible.
- Tighten spread only after clashes and required lessons are valid.
Why spread helps students
Regular subjects often benefit from touching several days: homework cycles, recall, and attention all improve when lessons are not stacked on one day. Block courses and intensive weeks are the exception.
Spread is usually a **soft** preference. Required lesson counts stay fixed; only the day pattern changes.
When spread fights other rules
A lab subject may need a double period. A part-time teacher may only work two days. A specialist room may be free on only three mornings. In those cases, some clustering may be the only valid outcome.
See soft constraints before you turn spread into a hard rule.
What to do next
- List subjects that should use more than one day per week.
- Exempt mandatory blocks, labs, and double periods from spread rules.
- Check teacher and room availability for each subject.
- Set a spread preference or minimum-day target per subject.
- Regenerate and compare spread against teacher gaps and room use.
- Document subjects where availability or blocks explain clustering.
Common mistakes
- Forcing spread on subjects that intentionally run as blocks
- Ignoring a scarce room that only exists on two days
- Raising spread until teacher workload or gaps become worse
Quick answers
Is lesson spread hard or soft?
Usually soft. The number of required lessons is fixed; the day pattern is often a preference.
Why are some lessons still clustered?
Blocks, availability, room limits, or stronger rules may leave clustering as the best valid outcome.