Why Kate Middleton Didn't Travel to See Queen Elizabeth in Scotland with Other Royals

The royal family rushed to Queen Elizabeth's bedside Thursday after Buckingham Palace announced her doctors were "concerned" for her health, but a key player was missing.

The Queen's granddaughter-in-law Kate Middleton did not join her husband Prince William for the journey north to the Balmoral Castle, the Queen's summer retreat in the Scotland. That's likely because it is the first day of school for the couple's three children, Prince George, 9, Princess Charlotte, 7, and Prince Louis, 4. The start of the new term is especially momentous for the young royals as they enroll as first-time pupils at Lambrook School following the family's move from London to Windsor at the end of the summer.

NOTTINGHAM - JUNE 13: Queen Elizabeth ll and Catherine, Duchess of Cambridge visit Vernon Park during a Diamond Jubilee visit to Nottingham on June 13, 2012 in Nottingham, England. (Photo by Anwar Hussein/WireImage)
NOTTINGHAM - JUNE 13: Queen Elizabeth ll and Catherine, Duchess of Cambridge visit Vernon Park during a Diamond Jubilee visit to Nottingham on June 13, 2012 in Nottingham, England. (Photo by Anwar Hussein/WireImage)

Anwar Hussein/WireImage Kate Middleton and Queen Elizabeth

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Hands-on mom Kate likely stayed behind at Adelaide Cottage for the children's first day of classes. However, Kate and the Queen spent quality time together just weeks ago, when the Duke and Duchess of Cambridge visited the 96-year-old monarch at Balmoral with their kids, a royal summer tradition.

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Queen Elizabeth II and Catherine, Duchess of Cambridge attend the annual Remembrance Sunday service at The Cenotaph on November 10, 2019 in London, England. The armistice ending the First World War between the Allies and Germany was signed at Compiegne, France on eleventh hour of the eleventh day of the eleventh month - 11am on the 11th November 1918.

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Though Kate will likely be known as Queen Consort when her husband takes the throne one day, it's unlikely that Queen Elizabeth has ever formally tutored her, as she is not one to hand down explicit "lessons," insiders say. Instead, historian Sarah Gristwood tells PEOPLE that the Queen may have approached her relationship with Kate the way she does with prime ministers.

Royal Family
Royal Family

Samir Hussein/WireImage Prince William, Kate Middleton, Prince George, Princess Charlotte and Prince Louis joined Queen Elizabeth and Prince Charles on the Buckingham Palace balcony on June 5.

"The Queen has always preferred to do rather than to say," says the author of Elizabeth: Queen and Crown. "With her audiences with her prime ministers, if there has been actual advice, it would be a discreet 'I think that went rather well' rather than actual instruction."

In an intimate sign of their close relationship, Kate regularly wears jewels on loan from the monarch and has followed her lead of wearing bright colors to be found in the crowd.

When the Queen's historic reign was celebrated this summer at the Platinum Jubilee weekend, the Duchess of Cambridge acted as envoy in Wales, rode in the first carriage of the prominent procession for Trooping the Color and joined the monarch on the balcony of Buckingham Palace as the festivities wrapped.

Prince William and Kate, both 40, "are representing the Queen impeccably," biographer Sally Bedell Smith previously told PEOPLE. "They're showing a kind of dedication she would be proud of. And that probably gives her hope."