A teacher may only be swapped if the code "(V) Variable teacher" has been activated. You can find this option on the "Codes" tab under "Lessons | Teachers". A teacher who is the cause of an optimisation bottleneck and for whom the code (V) is active may be replaced with another teacher.

As a rule, the code (V) applies to all the teachers of a lesson. Tick the option „Teacher allocation locked“ in the appropriate row in the lesson details window (under "Lessons | Teachers") if an individual teacher involved in the lesson should not be swapped under any circumstances. This deactivates the code (V) for this particular teacher in this coupled lesson (see example below).
