They grow up so fast! Reese Witherspoon celebrated a big milestone with her son Deacon this weekend — his elementary school graduation!

The Draper James founder, 40, shared an Instagram photo from the special occasion on Saturday, June 11. In the pic, 12-year-old Deacon — in a beige blazer, light blue shirt and checkered bow tie — beams alongside his mom, who wraps her arm affectionately around his shoulder.

Off to Jr High! Yay, Deacon! #proudmom

A photo posted by Reese Witherspoon (@reesewitherspoon) on

Witherspoon looks radiant in a pink floral dress, which she teamed with simple drop earrings and a huge smile. "Off to Jr High!" she captioned the sweet snapshot. "Yay, Deacon! #proudmom"

The Academy Award winner shares Deacon with her ex-husband, Ryan Phillippe. The pair also have a daughter, Ava, 16, and Witherspoon has a 3-year-old son, Tennessee, with current husband Jim Toth.

"My kids are wonderful," she told the Today show's Jenna Hager late last year. "They've been so supportive of what I do as a filmmaker, what I've been doing as an entrepreneur."

Like other kids their age, though, they sometimes find their mom a little embarrassing. (Just like Us!) "I like to have a dance party in the morning, 'cause I drink coffee and then I have lots of energy," Witherspoon told Hager. "And it's mortifying to my children."

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