Kate Middleton is preparing for Princess Charlotte’s new milestone after being forced to miss Prince George’s.

According to Hello!, Middleton is already prepping for another milestone of her daughter. Princess Charlotte will soon be joining her big brother Prince George at Thomas’s Battersea in London. Prince William and Middleton are expected to accompany Princess Charlotte on her first day of school on Thursday, Sept. 5.

Kensington Palace is also expected to release a couple of official portraits of Princess Charlotte in her school uniform. This is a tradition that the Cambridges have been doing. They did the same two years ago for Prince George, when it was his first day of school at Thomas’s Battersea.

They don’t do this annually. Last year, they didn’t release photos of Prince George because it was his second year. However, when it’s their children’s “first day” in school, Middleton would usually take the official photos of her children and share them wih the public to mark the event.

In 2017, Middleton was forced to skip Prince George’s first day of school since she was expecting Prince Louis. At the time, the Duchess of Cambridge was suffering from hyperemesis gravidarum and was advised to do a strict bed rest.

Prince George posed for his first day of school portrait with Prince William. In the snap, he looks cool and smart in his uniform. The third in line to the throne is all smiles as he holds Prince William’s hand and places his other hand inside his pocket. Middleton was visibly missing in the photo due to her health condition.

“Kate watched the news from home,” an insider said. “She was desperately sad that she couldn't make it but she is on firm bed rest now until she feels better.”

On Tuesday, the Duke and Duchess of Cambridge were spotted taking a budget plane back to London. Prince William, Middleton and their three children, Prince George, Princess Charlotte and Prince Louis, flew into Norwich Airport in Norfolk at 3:26 p.m. They were photographed getting off a Loganair plane from Aberdeen International Airport.

Prince William and Middleton were not able to wait for Prince Harry and Meghan Markle’s arrival in Scotland. The Duke and Duchess of Sussex won’t be joining the Queen in Balmoral Castle until next month.