Concentrate groups of lessons into fewer classrooms

For example the have 3 laboratories and Biology and Chemistry lesson2 can be in any of these. You can add this constaint that will specify that only 2 of these 3 laboratoris can be used on each day, for example to reduce cleaning costs:

Of course the above is more or less equivalent to removing one Lab from the school. But if you generate with relaxation allowed the above has two advantages:

1. if depending on other constraint it is not possible to use just 2 rooms, the software will relax this and use 3. If other constraints permit this, it will use 2.

2. more imporantly the relaxation works per days, this may produce a timetable where on most days you will use just 2 labs and only on a few days it will be necessary to use and clean all 3 labs.

Note:
-the affected labs were specified indirectly via the subjects that use them.
-add these constraints only after you see you can generate with 3 labs.