Constraint recipe
A subgroup split places parts of one class in different lessons at the same time, common for sets, option blocks, and practical rotations. Each taught subgroup needs its own teacher, room, and student list, and no student may sit in two parallel lessons at once. Build the membership data before placement, not after.
Key takeaways
- Define which students belong to each subgroup first.
- Parallel splits need a teacher and a room per taught group, in the same period.
- Rotations spread demand across weeks when rooms or kit cannot serve everyone at once.
- Option blocks need membership data before scheduling starts.
Structure before placement
Timetablers have names for these structures: parallel groups of one subject split by attainment are sets, subdivisions of a year group are bands, and choice subjects grouped for simultaneous teaching are option blocks, where each student takes one subject per block. Whatever your school calls them, a split is a data decision first: who is in group A, who is in group B, and whether the groups run at the same time or in rotation.
Without that structure, the timetable cannot prevent student clashes or reserve the right staff. Parallel splits consume more teachers and rooms in the same period; rotations spread the demand across weeks instead.
A worked example: one class, two parallel groups
Class 8C has 26 students and splits for craft subjects. Both groups run in the same double period, which is what makes the split expensive: two teachers and two specialist rooms at once.
| Subgroup | Students | Teacher | Room | When |
|---|---|---|---|---|
| 8C group A | 14 | Ms. Mäki | Workshop 1 | Tue P3+P4 |
| 8C group B | 12 | Mr. Aro | Textiles room | Tue P3+P4 |
Every student appears in exactly one row, which is the rule that prevents student clashes. If a third craft option existed but only these two rooms, the split would need a rotation instead: group C takes the workshop in week B, and the timetable alternates. See course catalog planning for how blocks, bands, and option structures are designed upstream of the timetable.
Build the split from the data up
- Export or build a student membership list for each subgroup, with every student in exactly one group per split.
- Decide whether the subgroups run in parallel or as rotations across weeks.
- Assign a teacher, room, and equipment to each taught subgroup for the same period, as in the table above.
- Place scarce-room and practical subgroups before flexible whole-class lessons.
- Recount each teacher's load: a split lesson is one lesson for the class but a full lesson for every teacher on it.
Split mistakes
- Creating subgroup names without a student membership list
- Scheduling parallel groups when only one eligible room exists
- Counting a split as one teacher load when it consumes two teachers
Quick answers
Do subgroups need separate teachers?
For parallel splits, yes. Each taught group needs its own teacher, room, and equipment at the same time.
Can subgroup splits run as rotations?
Yes. Rotations are the standard answer when room or equipment capacity cannot support every subgroup at once.