On: OptaPlanner – constraint solver for optimizing planning and scheduling problems

[panzagl]

I think he means a gap hour for the whole school- that you couldn't just put everyone in study hall all at once.

[ihaveajob → panzagl]

No, I meant a gap hour for an individual teacher. If they have 3 class hours but 1 gap hour in between, that reduces their schedule's flexibility.