Complex sentence: South Hampstead High School is an independent day school in Hampstead, north-west London, England, which was was founded and is still supported by the Girls' Public Day School Trust (GPDST).
Split into simpler sentences: South Hampstead High School is an independent day school situated in Hampstead, north-west London, England. The school was founded and is still supported by the Girls' Public Day School Trust (GPDST).