Sassoon was born on 2 September 1936 in Surabaya on the island of Java in what was then the Dutch East Indies and is now Indonesia.
Her first exposure to ballet was when she was five years old, when her mother took her to the War Memorial Opera House in San Francisco to see Romeo and Juliet by Sergei Prokofiev.
At the age of 16 she moved to Paris, where she trained with teachers such as Leo Staats, Lubov Yegorova, Olga Preobrajenska and Mathilde Kschessinska.
[1][2][3] Sassoon began dancing in public at the Grand Ballet du Marquis de Cuevas in Paris in 1952, staying there until 1955.
[1][2][3] Sassoon's father established the Academy of Ballet at 2121 Market St. in San Francisco in 1953 to offer training for children, adults, students preparing for a professional career and others.