Complex sentence: Father Armstrong and Father Kabvuma (originally from Uganda) served as priests at the school during the late 1970's and early 1980's and during this period the school only covered up to Standard 4 (Grade 6).
Split into simpler sentences: Father Armstrong and Father Kabvuma (originally from Uganda) served as priests at the school during the late 1970's and early 1980's. During this period, the school only covered up to Standard 4 (Grade 6).