Complex sentence: During the time of British Headmasters Sir F. Tydd and Mr. Sinclare, the school had started blooming it's petals, but it's total break out in educational, social and cultural field took place during the age of Rajnarayan Bose.
Split into simpler sentences: During the time of British Headmasters Sir F. Tydd and Mr. Sinclare, the school had started blooming it's petals. But the total break out of the school in educational, social and cultural field took place during the age of Rajnarayan Bose.