Student Restrictions

Restrictions (also called mismatches) let you define pairs of students who should not be placed in the same classroom. They are the opposite of preferences, which pull students together. Restrictions push students apart.

What Are Restrictions?

A restriction is a rule that tells the algorithm two specific students must end up in different classrooms. When you create a restriction between Student A and Student B, the system treats it as a hard constraint — it will not place them together under any circumstances.

Think of restrictions as separation rules. While preferences say "keep these students together," restrictions say "keep these students apart."

When to Use Restrictions

Common scenarios where restrictions are helpful:

Behavioral conflicts — Two students who consistently disrupt each other or have a history of conflict that makes classroom management difficult.
Negative social dynamics — Pairs whose interactions negatively affect the learning environment for themselves or others.
Siblings or twins — Many schools prefer to separate siblings into different classrooms so each child can develop independently.
Teacher or parent requests — Specific separation requests backed by professional judgment or documented concerns.
Distraction patterns — Students who tend to distract each other even without overt conflict, reducing focus and engagement.

How to Set Restrictions

To create a restriction between two students, start with at least two students in the roster. If the roster is too small, Shibutz directs you back to Students before you add restrictions:

Navigate to the Restrictions section in your placement workspace.
Select the first student from the dropdown list.
Select the second student you want to separate from the first.
Click Add Restriction to save it.

Restrictions are bidirectional. Adding a restriction between Student A and Student B automatically prevents both from being in the same classroom — you only need to add it once.

Conflict Detection

When you add a restriction, the system automatically checks for conflicts before saving the pair:

Match-mismatch overlap — If the same pair already exists in preferences, an error blocks the submission. A pair cannot be both kept together and kept apart.
Separation clique overflow — If adding the restriction creates a group of mutually-separated students larger than the number of classrooms, a warning is shown. The algorithm cannot place them all in different classrooms.
Required placement conflict — If both students already have required placements in the same classroom, a warning notes the restriction cannot be fulfilled.

Warnings still allow you to add the pair but inform you of potential issues. Errors must be resolved before the restriction can be saved.

Restrictions vs. Preferences

It is important to understand how restrictions differ from preferences:

Preferences are soft constraints — the algorithm tries its best to honor them but may not fulfill every request if doing so would compromise overall balance.
Restrictions are hard constraints — the algorithm will always keep restricted pairs apart. A valid placement never places two restricted students in the same classroom.

Because restrictions are strictly enforced, adding too many can make it harder for the algorithm to find a balanced solution. Use them only when separation is genuinely necessary.

How Restrictions Affect the Algorithm

During placement generation, the algorithm processes restrictions as hard constraints before optimizing other factors such as gender balance, scale distribution, and friend placement. This means:

Restricted pairs are guaranteed to be in separate classrooms.
The more restrictions you define, the fewer valid arrangements exist, which can limit how well the algorithm balances other criteria.
If restrictions conflict with required placements, the algorithm may not be able to find a valid solution at all.

Tips

Only add restrictions for pairs where separation is essential. Overuse can reduce placement quality.
Review restrictions each year — dynamics change as students mature.
If generation fails, check the Constraint Health card on the workspace overview page for the same readiness checks used by the Generate button — the system proactively flags blocking setup issues, overlapping restrictions, clique overflows, and required-placement issues.
You can delete a restriction at any time before generating a placement.

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