Children can come to the school on second period, but only once per week

1. First you need to allow that students can arrive on the second period:
Blok vyučovania - umožňuje niektorým triedam neskorší príchod alebo skorší odchod.

2. Then you can limit how many times this will happen by advanced card relationship that says that class has to have at least 4 lessons on period 1: