Complex sentence: The centenary celebrations of the pathashala were held in 1972 and it was decided to start a high school following which the Sadvidya High School was opened in 1973-74, and in 1999 the Sadvidya Composite Pre-university College was added to provide tertiary education.
Split into simpler sentences: The centenary celebrations of the pathashala were held in 1972 and it was decided to start a high school following which the Sadvidya High School was opened in 1973-74. In 1973 it was expanded to provide high school education, and in 1999 the Sadvidya Composite Pre-university College was added to provide tertiary education.