Bahrain underwent a period of major social reform between 1926 and 1957, under the "de facto" rule of Charles Belgrave, the British advisor to Shaikh Hamad ibn Isa Al-Khalifa (1872-1942). The country's first modern school was established in 1919, with the opening of the Al-Hiddaya Boys School, while the Persian Gulf's first girls school opened in 1928. The American Mission Hospital, established by the Dutch Reform Church, began work in 1903. Other reforms include the abolition of slavery, while the pearl diving industry developed at a rapid pace.