Prince Louis celebrated his third birthday in a big way

Prince Louis has checked off a royal right of passage: his first day of school photo!

Like older siblings Prince George, 7, and Princess Charlotte, 5, Prince Louis's first day of nursery school wasn't complete without a picture marking the milestone. Like many proud parents, Kate Middleton was behind the camera for all three of her children's school portraits.

While Prince George looked a little nervous for his first day of nursery school at Westacre Montessori in Jan. 2016, Prince Louis, who started preschool last Wednesday, sported a giant grin just like big sister Charlotte did on the steps of Kensington Palace ahead of her first day in Jan. 2018.

Just like his royal siblings, Prince Louis sported a backpack for the big day.

Royals first day of nursery school
Prince Louis; Prince George; Princess Charlotte
| Credit: The Duchess of Cambridge/Kensington Palace via Getty (3)

In a unique twist, Prince Louis posed on a red walker bicycle.

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The young prince is attending London's Willcocks Nursery School, the same school Princess Charlotte attended near the family's Kensington Palace home in London.

A royal source told PEOPLE at the time, "They chose that nursery because they thought it would be an ideal first step for Charlotte's education, and they were impressed by the team who work there."

The nursery school is the perfect choice for Louis given that Prince George and Princess Charlotte both attend Thomas's Battersea nearby.

Both George and Charlotte began nursery school in January, but Louis's later start date was likely affected by the latest lockdown in the U.K. amid the ongoing COVID-19 pandemic.

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The latest photo of Prince Louis doubled as both his first day of school snap and his third birthday portrait.

"The Duke and Duchess of Cambridge are delighted to share a new photograph ahead of Prince Louis' third birthday tomorrow," Kensington Palace said in a statement on Thursday.