The Good Schools Guide describes Thomas's Battersea as "a big, busy, slightly chaotic school for cosmopolitan parents who want their children to have the best English education money can buy."
William got his start at Jane Mynors' nursery school and the pre-preparatory Wetherby School, both in London.
Kate was unable to attend George's first day of school as she is suffering from hyperemesis gravidarum, which was severe enough during her first pregnancy to land her in the hospital.
Thomas's Battersea students are expected to leave with a "strong sense of social responsibility," continue on a path to become "net contributors to society," and also to "flourish as conscientious and caring citizens of the world."
The family's move to London coincides with the Duke and Duchess' decision to make Kensington Palace their main residence.
One cameraman and one photographer were at the school to document George's first day, as William had asked the press to respect his son's privacy.
George's grandfather, Prince Charles, was first educated at home by a governess, but later attended the Cheam Preparatory School in Berkshire.
George has joined a class of 20 other students and has his own desk with a name plate.