Complex sentence: All the government schools in the district are taught in the Pashto language primarily with a subject in Farsi/Dari; it has been this way for decades since the majority of the population are Pashtuns.
Split into simpler sentences: All the government schools in the district are taught in the Pashto language primarily with a subject in Dari. It has been this way for decades since the majority of the population are Pashtuns.