Atgal   We would like that some subjects take place one after the other in the parallel classes. For example, the first lesson in class 9A is physics, while at the same time class 9B has chemistry, and then the second lesson for 9A is chemistry and for 9B – physics. It is convenient if we need to make two hours long tests or exams  – then we do not need to change the timetable


For these subjects two additional relations should be added:

For example, for 9th grade classes physics:

  1. Maximum number of days per week: 2 (should be equal to the number of lessons per week). Choose needed subject – physics, classes, teacher.


  1. The maximum number of windows (gaps) per day – 0. Choose subject physics, classes, teacher.


The program then places the lessons as follows: for example, on Monday the second lesson for 9A and the third lesson for 9B – physics. On Wednesday physics is first for 9B and second for 9A.

As we set that there should be no windows between lessons of physics for 9th grade classes, physics lessons will follow one another.

Set the same relations to chemistry.

Another approach: to create two periods-long lessons (double lessons) of physics and chemistry for 9-th classes, assigning them two teachers and two classrooms. Then during first hour could be physics lesson for 9A and chemistry for 9B, and during second hour – chemistry for 9A and physics for 9B.