1 of 41
"First day of school for Rafa...not sure how we feel about it yet," wrote Hilaria Baldwin, captioning a pic of her adorable son.
2 of 41
So sweet! "How we feel about Willa Gray's first official day of school," captioned mom Lauren Akins, posting a father-daughter photo of her child with country crooner Thomas Rhett.
3 of 41
SKYLER & KAIUS
"Major moment this week...huge," Rachel Zoe captioned this sweet pic of her two boys.
4 of 41
It's impossible for Lucy Liu's adorable son, who she calls "Boss" on Instagram, to be any more adorable on his "first day of school ever!"
5 of 41
BROOKS & SCARLETT
"First day of school!" wrote Molly Sims, captioning a photo of her kids. "Momma is taking it pretty hard this morning!"
6 of 41
Eva Amurri is one proud mom! The lifestyle guru celebrates with a sweet pic of her daughter on her first day of preschool.
7 of 41
Fuller House star Marla Sokoloff can hardly keep it together as her youngest daughter prepares for her first day of preschool on Sept. 7. "DON'T WORRY ABOUT ME I'M TOTALLY FINE," she wrote on Instagram, adding the hashtags: "#imnotcryingyourecrying" and "#actuallyimcrying."
8 of 41
SAMUEL & ALEXANDER
Naomi Watts' kids squeeze in some goodbye cuddles before heading to their first day of school.
9 of 41
BROOKLYN & CAMDEN
Nick and Vanessa Lachey's kids are pumped as can be to attend preschool.
10 of 41
EMME & MAX
It's been an emotional day for Jennifer Lopez, who shared her twins are starting their first day of fourth grade. "So proud of my babies..." she wrote on Instagram.
11 of 41
"Totally faking that smile because this morning he gathered all the words he knew so he could tell me that he couldn't go to school because pirates were coming with swords and he needed to stay home to eat a bagel with cream cheese," The Kitchen star Marcela Valladolid wrote on Instagram, captioning a pic of her son.
12 of 41
On his first day of school, the 10-year-old actor pledged to "choose kind" and encouraged his fans to do the same. "Let's pledge to choose kind so students from all walks of life can feel accepted and free to express and develop their individuality," Tremblay said. "Let's pledge to choose kind so my school and all of your can be a kind place."
13 of 41
"Every single emotion pouring forth!!!" wrote Casey Wilson of her son's first day of Preschool.
14 of 41
Where did the time go? Kelly Ripa's youngest son is all smiles as he gears up for his first day of high school.
15 of 41
Katherine Heigl's daughter gets ready for her first day as a Kindergarten student.
16 of 41
HANK & ALIJAH
Kendra Wilkinson Baskett's eldest child, Hank, poses with his little sister before embarking on his first day of second grade.
17 of 41
Alyssa Milano's son is as excited as ever to start Kindergarten. "Ready for a great day!" captioned the former child star.
18 of 41
"Harper, you are kind, sweet, caring, smart, silly and fun and you make your daddy and I so proud," wrote Tiffani Thiessen of her daughter, who is a newly minted second grader.
19 of 41
"From nearly dying at birth to standing on the steps of Preschool," wrote Kyle Newman of his and wife Jaime King's eldest son. "Excited to watch you grow."
20 of 41
BAKER & GRIFFIN
"So... my sweet babies started school today," wrote Leigh-Allyn Baker on Instagram.
21 of 41
HONOR & HAVEN
"First Day of School!" wrote Cash Warren, captioning a pic of his and wife Jessica Alba's daughters. "This is how our convo rt before this photo 'so girls, if your teachers ask...Haven we practiced your reading for 20 mins a day over the summer and Honor we practiced your multiplications. K?' 'We can't lie Dad!!' 'Oh, you certainly can if you like your iPads. Have a great first day! Love you so much' #parenting101"
22 of 41
Jessica Simpson's daughter strikes a pose before embarking on her first day of Kindergarten.
23 of 41
Roselyn Sanchez's daughter is growing up! Here, the Kindergarten student pictured with a sign depicting her interests, hobbies and future goals.
24 of 41
He's a big boy now! Lindsay Price's son rocks out before taking on his first day of Kindergarten.
25 of 41
Kevin Federline's wife Victoria not only documented their daughter's 6th birthday on Aug. 15 but also her first day of first grade.
26 of 41
CHARLOTTE & ROCKY
Sarah Michelle Gellar and Freddie Prinze Jr.'s son helps send off his big sister as she starts second grade. "And just like that ... one is back in school!!" Gellar wrote on Instagram, adding: "Second one wishes he was."
27 of 41
MASON & BRAYDON
"And they are off.... one in each school this year. Everyone is on their own this year which is character building but gonna be tough for all of us," Melissa Joan Hart wrote, captioning pics of her backpack-clad sons. "Can't believe the summer flew by so fast!"
28 of 41
"Bye-bye summer! 1st day of school on my way 2 pick up my babies, so excited!" wrote Brooke Burke-Charvet. "Not sure who had a harder time separating today me or them."
29 of 41
DOLLY & CHARLIE
Rebecca Romijn's twin daughters are more than ready to take on the third grade!
30 of 41
"It's this gorgeous girls first day of 3rd Grade!" wrote Katherine Heigl of her daughter's big day. "Can't believe summer is already over & my baby is a 3rd grader! Time flies that's for sure."
31 of 41
MAXWELL & BLAKESLEY
Bachelorette star Trista Sutter snaps a pic of her children on the first day of fourth and third grade, respectively. She also shares her two kids' career aspirations, with Maxwell hoping to one day become a shark biologist and Blakesley, a veterinarian.
32 of 41
Like father, like son! Ty Murray's son shows off his dad-approved outfit (which Kase picked out himself!) with the cowboy's girlfriend Paige on his first day of Kindergarten.
33 of 41
Mario Lopez's daughter strikes a pose on her first day of first grade. "Gia ready to tackle 1st grade!" wrote the Extra host.
34 of 41
It was the first day of school for Marcelo and in case you were wondering, mom Ali Landry definitely got emotional. "Yes, I totally cried!!!!!" she wrote on Instagram.
35 of 41
Jamie Lynn Spears' daughter is all smiles as she poses with her dogs on her first day of fourth grade.
36 of 41
EVERLEIGH, ARMIE & RECKER
Equipped with backpacks and smiles, Cam Gigandet's kids are more than ready to conquer the first day of school.
37 of 41
BEATRIX & ZOIE
"Happy first day of school to these two awesome little ladies!! I am so proud of them! Although, I can't believe they're in 4th and 2nd grade!!" Fuller House star Jodie Sweetin wrote of her daughters Zoie and Beatrix, respectively. "How did that happen?!"
38 of 41
AJ McLean is one proud papa! The Backstreet Boys member documented his daughter's orientation day before kicking off her first day of Kindergarten. "She's so excited and I couldn't be more proud!!!" he tweeted.
39 of 41
Race car driver Jimmie Johnson can't help but be excited for his daughter, Genevieve, who is now a newly minted first grader. "Official big girl status," he captioned the adorable pic.
40 of 41
Evan smiles at mom Jenny McCarthy as the radio personality wishes her son a great first day of high school. "First day of high school drop off," she tweeted. "So proud."
41 of 41
CARMEN & VINCENT
Olympic gymnast Dominique Moceanu celebrates her kids' first day back to school.
Headed to Hogwarts! PBteen Launches Harry Potter Collection That'll Turn Your Child's Room into a Wizard Wonderland
Nikki Reed on Deciding to Start a Family: Husband Ian Somerhalder 'Threw Out All My Birth Control Pills'
See How Jaime Pressly Will Cover Up Her Twin Pregnancy on Mom: 'I Knew They Would Come Up with Something Fantastic'
Darnell Nicole’s Blog: How I Handle Co-Parenting My Daughter with My Ex a Year After Our Split
Romeo! Julia! Preston and Jayden! See Which Celeb Babies Celebrate Their Birthdays in September