Complex sentence: PPSK (Catholic School Student Union) is the pioneer of OSIS (School Student Union) in future time, where the Canisius branch was quite active during the 1952-1967 period.
Split into simpler sentences: PPSK (Catholic School Student Union) was the pioneer of the future OSIS (School Student Union). The Canisius branch was quite active during the 1952-1967 period.