Princess Charlotte, daughter of Prince William and his wife Kate, started school on Thursday, joining her elder brother Prince George at Thomas’s Battersea in southwest London.

Four-year-old Charlotte, dressed in the school’s uniform of navy blue with red trim cardigan and blue skirt, held her mother’s hand as she arrived at the school, accompanied also by her father and her brother.

Strict about children’s appearance, the London school emphasizes that hair longer than shoulder length must be tied back. Charlotte had done so neatly, with a wispy ponytail. She also bore a backpack with a sequin-studded unicorn keychain.

Headteacher Helen Haslem greeted Charlotte with a handshake as the princess balanced on tip-toe to introduce herself, watched by a beaming Duchess of Cambridge, who wore a modest floral dress.

Watch as Charlotte arrives for her first day of school:

Princess Charlotte, daughter of Britain’s Prince William and his wife Kate, joined her elder brother Prince George at Thomas’s Battersea in southwest London. 0:47

The great-granddaughter of Queen Elizabeth, Charlotte is fourth in line to the throne, after — in ascending order — five-year-old George, her father William and her grandfather Prince Charles.

Charlotte’s younger brother, Louis, who is fifth in line to the throne, celebrated his first birthday in April.

George has been a pupil at Thomas’s Battersea since 2017.

The school teaches 560 boys and girls between ages four and 13, with yearly fees for each four-year-old of around $24,000 US.

The tuition for Charlotte, however, will be discounted because her brother is already a pupil.

Two years ago, police reviewed security arrangements at the school after a 40-year-old woman was arrested on suspicion of attempted burglary shortly after George started.

The woman accepted a caution for causing a nuisance on school property.