This back-to-school season is a bittersweet one for Naomi Watts and Liev Schreiber.

The former couple, who share son Sasha and daughter Kai, revealed that Sasha left home for college in emotional tributes shared on Instagram. The 18-year-old, Watts and Schreiber’s first child, is attending the University of Southern California.

In an Aug. 20 post, Watts shared a series of photos of herself and Schreiber helping Sasha move into his dorm, which included a sweet group shot of the family sitting together in Sasha’s bed.

“We packed and unpacked, stacked, and color coded. We walked and walked, woke up early with excitement. Then we shopped and shopped and sometimes fought about stupid stuff,” Watts, 56, wrote.

She continued: “We laughed, we cried, I had a few extra secret cries and maybe some not-so private ones. We hugged a lot. We built things, we talked to robots, we ate good food. We got lost a bunch. We met so many great people.”

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Watts and Schreiber welcomed Sasha in July 2007, two years after the couple began dating. Watts paid tribute to her son in a July 25 Instagram post for Sasha’s 18th birthday.

“18 today and ready for the world! Cannot believe it. 😊😭” Watts wrote at the time. “Have so loved watching you grow into the kindest, most wonderful young man. Thank you for making me a first-time mum. ♥️”

While the teen’s milestone proved to be emotional for Watts, the Oscar-nominated actress reminded herself, “he’s got this!!”

“He did it!! He dreamed big and worked really hard for something wonderful,” Watts concluded. “Go @sashapeteschreiber — we love you so much.”

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Liev Schreiber pays tribute to ‘ride or die’ Sasha Schreiber

Despite the pangs of letting go, Schreiber is a proud poppa.

The Emmy-nominated actor gushed over son Sasha in an Aug. 17 Instagram post ahead of the teen’s first day of school.

“Starting to feel the pull. Gonna miss my ride or die,” Schreiber, 57, wrote alongside a photo of the father-son pair. “Having said that, USC is gonna get one of the deepest, kindest, bravest, and most beautiful boys I have ever known.”

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Sasha, alongside mother Watts, accompanied Schreiber to the 30th Critics’ Choice Awards in February, where “The Perfect Couple” star received the award for best supporting actor in a limited series.

“So proud of my pops for this great accomplishment!” wrote Sasha on Instagram, jokingly adding: “(And mom for trying).”