"We're both NOT happy about this!!!" Vanessa Lachey wrote Wednesday, sharing a photo of daughter Brooklyn looking pouty on her first day of school

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Credit: Vanessa Lachey/Instagram

Growing up is hard to do — just ask Brooklyn Elisabeth.

Vanessa and Nick Lachey‘s 3½-year-old daughter is adorably pouty in an honest photo her mom posted to Instagram Wednesday, sitting on the family’s front stoop with her head down and her hands between her knees.

Posing next to a sign reading, “Brooklyn’s 1st day of 4 yr. old preschool” alongside the date, the little girl looks ready for a day of learning regardless of her expression, wearing a cute bunny-pattern outfit, a red bow, gold Mary Janes and socks with a pencil-like design.

“We’re both NOT happy about this!!! 😩🎒📚 #BrooklynElisabeth,” Vanessa, 37, captioned the memorable snapshot, also showing off Brooklyn’s sweet (and affordable!) unicorn backpack by Skip Hop ($17.50).

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Camden Lachey
| Credit: Vanessa Lachey/Instagram

The precious photograph comes exactly one week after Brooklyn’s big brother Camden John, 6 next week, headed off on his first day of kindergarten.

Sharing a series of snapshots presumably taken by Vanessa, the 98 Degrees singer, 44, posed with a smiley Camden while the latter wore a sports-themed backpack and a blue-and-khaki school uniform.

The second image showed the father-son pair sharing a sweet smooch, while the third featured a cringing Camden pushing his dad’s face away.

“My high & low for today: my son’s first day of [kindergarten], definitely a HIGH! Apparently also my last day for public kisses. Swipe ➡️😩 #proudpapa,” Nick captioned his post.

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Mom Vanessa couldn’t help sharing her own tribute to her oldest child as he went off to begin his new academic adventure, posting a photo of herself hugging Camden and a second of him posing next to a sign that read, “Camden’s 1st day of kindergarten,” alongside the date.

“It’s official, my first born is now off to his first day of Kindergarten,” she began her lengthy caption. “I’ll never forget our first skin to skin, his first hiccup, his first social smile, his first word (Dog), his first joke, his first ‘I Love You, Mama’ and now his first day of school. I still have so much to look forward to, his first serious question, his first girlfriend, his first time driving, his first broken heart (she better watch out!), his first day on his own in the real world and the first time he realized how we did it ALL for him and he says ‘Thank You.’ ”

“Even if he doesn’t, I am so proud of this little guy and can’t wait to see the man he will become,” the mom of three added. “Camden John Lachey, the world is your oyster! To the moon and back and back again!!! Forever & Always … my baby boy!!! 💫❤️💋”