It's back to school for Britain's royal family, and this year marks Princess Charlotte's very first day. The 4-year-old arrived at Thomas's Battersea in London Thursday morning with her family.

Charlotte, fourth in line to the throne, had older brother Prince George, 6, as company as she started school. Both of their parents, the Duke and Duchess of Cambridge, dropped them off. William and Kate's third child, Prince Louis, wasn't present.

Kensington Palace shared a sweet video of the family's arrival to mark the occasion.

Princess Charlotte arrives for her first day of school at Thomas’s Battersea, joining her older brother Prince George. ✏️📚🏫 pic.twitter.com/8l63WEjzcw — Kensington Palace (@KensingtonRoyal) September 5, 2019

Charlotte donned the school's navy blue and red uniform, but added a personal touch to her backpack; a pink unicorn keychain.

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The head of the lower school, Helen Haslem, greeted the royal family as they arrived. Prince William told her that Charlotte was "very excited" to start.

The princess smiled and shook Haslem's hand as the head teacher asked about her summer.

Prince George, third in line to the throne, has attended the London private school since 2017.