Almost every school running the IB Diploma Programme has a subject that might not run. A small HL class in a language, an arts subject with a handful of students, a second science that splits a cohort. The question is not whether this will happen, but when you find out. Discovering a non-viable class in June is an administrative task; discovering it in September is a problem for students, teachers and leadership. This article covers how to set minimum group sizes, how to see the numbers early and how to handle subject levels that fall short.
Why minimum group sizes matter
Each class costs teaching time, which means staff contracts, rooms and timetable slots. A DP subject at HL has a recommended 240 teaching hours over the two years and at SL 150 hours, so a single small class can represent a significant share of a teacher's load.
Leadership usually has a view, explicit or not, on the smallest class the school can afford. Making it explicit before choices open helps everyone:
- Leadership can plan the budget and staffing with fewer surprises.
- Coordinators have a clear rule to apply rather than negotiating case by case.
- Students and families know from the start that a subject level may not run, and why.
Setting separate SL and HL minimums
A single minimum per subject rarely reflects reality. SL and HL often have different economics and different teaching arrangements.
Why separate minimums
- HL classes have more teaching hours, so a small HL class costs more than a small SL class.
- Some schools teach SL and HL together for part of the time; the combined group can make a smaller HL count acceptable.
- Demand differs: a subject may be popular at SL and rare at HL, or the other way round.
A worked example
| Subject level | Minimum | Reason |
|---|---|---|
| Biology HL | 5 | Combined teaching with SL for shared content |
| Biology SL | 6 | Standard school minimum |
| Visual arts HL | 4 | Strategic subject the school wants to keep |
| Economics HL | 6 | Standard school minimum |
| Economics SL | 6 | Standard school minimum |
These numbers are illustrative; your school's figures depend on budget, staff and policy. What matters is that each subject level has its own number and that the reason is written down.
Who decides
Agree the minimums with leadership before the window opens, and record any exceptions. A subject that runs below its minimum for strategic reasons should be a documented decision, not something that happens because nobody checked.
Seeing viability during the window, not after it
The most effective change most schools can make is to track viability while choices are open, rather than counting at the deadline.
Live counters
Show, next to every subject level, how many students have chosen it against its minimum. For example:
- "HL 11/5 – the subject will run"
- "SL 3/6 – 3 more students needed"
When students, teachers and the coordinator all see the same numbers, conversations happen earlier. A student torn between two subjects can see that one of them is short; a tutor can mention it during a one-to-one.
What to watch
During the window, review weekly:
- Subject levels below their minimum, sorted by how far they are from it.
- Subject levels just above their minimum, which could fall below if one or two students change.
- Students whose current choice includes a subject level below its minimum.
A filter showing only subject levels below the minimum makes this a five-minute task.
Communicating with students and families
Clear communication prevents most complaints. Explain the rule at the information evening and in writing:
- every subject level has a minimum number of students;
- subject levels below the minimum at the deadline may not run;
- students affected will be asked to choose again during a corrections round;
- the school will tell affected students by a specific date.
Avoid promising that a subject will run before the numbers are known. Instead, suggest that students think about a second-best option for any subject that looks marginal. Reminders before the deadline should go both to students with incomplete choices and to students whose choice includes a subject level that is still below its minimum.
Running the corrections round
After the deadline, leadership confirms which subject levels will not run. Then open a short corrections round.
Restrict the moves
In the corrections round, allow students to move only to subject levels that already reach their minimum. Without this restriction, students leaving one non-viable class can spread across other small classes, and you end up with new non-viable groups.
Check the knock-on effects
Changing one subject can break other rules: the HL/SL count, an exclusion or a prerequisite. Every corrected choice must be validated again, exactly as at the original submission. See validating DP subject combinations for the rules worth checking.
Record every change
Keep a history of who changed which choice and when. It protects the school if a family later disputes a change, and it gives you an accurate picture for next year's planning.
Using minimums when planning blocks
Minimums also affect the timetable. When you sketch option blocks, decide whether to include subject levels below their minimum in the draft. Including them shows the full picture; excluding them shows the timetable you are most likely to run. Trying both is often useful, as described in from DP subject choices to option blocks.
Checklist
- Separate SL and HL minimums agreed with leadership for every subject.
- Exceptions recorded with a reason.
- Rule explained at the information evening and in writing.
- Live counts against minimums visible during the window.
- Weekly review of subject levels below and just above their minimum.
- Reminders sent to students whose choice is below a minimum.
- Decision on non-viable subject levels taken and communicated by a fixed date.
- Corrections round limited to subject levels that reach their minimum.
- Every corrected choice validated again.
- Change history kept.
Frequently asked questions
Should the minimum be the same for all subjects?
Not necessarily. A school may accept a smaller group in a subject it considers strategic, or in an HL class taught partly with SL. The important thing is that each exception is a deliberate, recorded decision.
What if a subject is one student short at the deadline?
That is a leadership decision: run it, merge it, or close it. Live counters during the window make this situation rarer, because students and tutors can see the shortfall early.
Do students see other students' names?
They do not need to. Showing counts against the minimum gives students the information they need without exposing who chose what.
See MyIB with your own subjects
MyIB is independent IB subject selection software for schools running the IB Diploma Programme. It lets you set separate SL and HL minimums, shows live quorum counters to students, teachers and the coordinator, sends reminders to students with incomplete choices or choices below a minimum, and limits the corrections round to subject levels that will run. Book a demo or see pricing; the first subject-choice cycle can run as a free pilot.