William, Kate recently moved into Adelaide Cottage in Windsor to be closer to their children's new school
As the royal family rushed to the Balmoral castle in Scotland to be with Queen Elizabeth, Kate Middleton stayed back with her children in England, at Windsor.
Queen Elizabeth, Britain's longest-serving monarch, died on Thursday at 96 after a 70-year reign.
While Prince William, like Charles and Camilla, flew to Scotland, Kate Middleton, the Duchess of Cambridge, stayed at Adelaide Cottage and was spotted leaving Windsor Castle to pick up her children from school.
"The Duchess of Cambridge has remained in Windsor as Prince George, Princess Charlotte and Prince Louis are on their first full day at their new school," a statement from Kensington Palace said.
Yesterday was the first day for Prince George, Princess Charlotte and Prince Louis at Lambrook School.
A day before, the Cambridges arrived at the school for a "settling-in day".
In photos, the family was seen smiling as the children met headmaster Jonathan Perry.
William and Kate moved into the four-bedroom Adelaide Cottage in Windsor last Saturday to be closer to their children's new school, which is about 20 minutes from their home. All three children will go to the same school for the first time.
On Thursday, as Queen Elizabeth's doctors expressed concern over her worsening health, the royals headed to Balmoral to be at the monarch's bedside.
Prince Harry also left alone for Scotland, leaving wife Meghan. The Duke and Duchess of Sussex were to attend the WellChild awards in London last evening but cancelled the plan.
Prince William will likely become the Prince of Wales and his wife, Kate Middleton, the Princess of Wales, following the death of Queen Elizabeth on Thursday. Prince William held title of Duke of Cambridge before the Queen's death.
The title 'Prince of Wales' is reserved for the heir apparent and was held by Charles, now King. The title of 'Princess of Wales' was last held by Princess Diana because Duchess Camilla, wife of Charles, chose not to use it out of respect.