Oliver James Montgomery-Good Luck Charlie Star Mia Talerico Is All Grown Up in High School Sophomore Year Photo

Good luck in high school,Oliver James Montgomery Mia Talerico!

After all, the Good Luck Charlie star—who played the titular toddler on the Disney Channel show—started her sophomore year on Aug. 19.

To mark the occasion, Mia shared photos of herself during her first day of class, joking on Instagram, "Cue the comments about feeling old."

And just as the 15-year-old predicted, fans couldn't get over just how quickly she's grown up in front of their eyes, with one quipping, "You’re right we do feel old."

"You were just a baby!! I was just a baby!!" a second Instagram user commented. "And since you’re now a sophomore, I’m definitely getting old!"

Meanwhile, a third fan pointed out that Mia is around the same age her onscreen sister Teddy—played by Bridgit Mendler—was when she "started making the video diaries" for Charlie.

"That’s insane," the fan added, "but so amazing and wonderful to see!!"

Also starring Bradley Steven Perry, Jason Dolley, Leigh-Allyn Baker and Eric Allan Kramer, Good Luck Charlie ran for four seasons from 2010 to 2004. The sitcom centered around the Duncan family, with events from each episode providing material for a video diary intended to be given to baby Charlie when she is older.

Last year, Mia reunited with her onscreen brother and dad—played by Bradley and Eric, respectively—to make an Italian dinner together. While cooking shrimp scampi, the trio even recreated the iconic photo of Bradley and Eric holding Mia upside down.

"Whoa," Bradley later wrote on Instagram. "Time flies, huh?"

So, what's the rest of the Duncan family up to these days? After playing a teen on the show, Bridgit is now a mom to a son who will soon be heading to school of his own.

"I'm a mama to a sweet 4yo boy," she shared on X, formerly known as Twitter, on Feb. 19. "Started fostering in 2021 adopted near Christmas of 2022. I’m so lucky—being a parent is the biggest gift and most defining experience there is."

To see more celeb kids heading back to school, keep reading...

Time flies when you're keeping up with the Kardashians! Case in point: The reality star was having "a really hard time processing the fact" that her daughter True Thompson—who she shares with ex Tristan Thompson—was heading into the first grade. 

"There’s this undeniable feeling that I’m losing parts of who she was with each day that passes," Khloe wrote on Snapchat Aug. 26. “Time moves fast, faster every year it feels like, and this new school year is a reminder to me to fully embrace every moment and soak it all in.”

The country singer and her husband Eric Decker's three older kids—Vivianne, 10, Eric II, 8, and Forrest, 6—returned to school on Aug. 19. 

And with baby Denver at home, Jessie wrote on Instagram, "I still can’t believe I have a middle schooler and a 6month old."

Back to school season was off to a shining start for the model and Nick Cannon's son Golden Sagon, who started the fourth grade at just 7 years old after skipping kindergarten and pre-K.

Meanwhile, Golden's sister Powerful Queen—who Nick also shares with Brittany—began pre-kindergarten.

As the Good Night, Sister author and her husband Chris Pratt prepare to welcome baby No. 3 together, their daughters Lyla and Eloise headed off to their first day of class.

Katherine captioned this Aug. 18 photo of the girls wearing their custom Stoney Clover backpacks, "How is it already back to school time?!"

Britney Spears' nieces are growing up fast! Maddie—who Jamie Lynn shares with ex Casey Aldridge—began her junior year of high school.

Meanwhile, Ivey—who the Zoey 101 alum shares with husband Jamie Watson—became a first grader.

The Saved by the Bell alum sent kids Gia, 13, Dominic, 10, and Santino, 5, off to school on Aug. 20, joking that means he and wife Courtney Lopez "have homework" to do.

"One (and only) year with all 3 kids at the same school," Courtney added in an Instagram post of her own. "So excited to wake up earlier, make lunches they won’t eat and do homework I can’t understand!"

The Teen Mom: The Next Chapter star embarked on not one, but two new chapters when her and ex Corey Simms' twins Aleeah and Aliannah started high school, and her youngest daughter Adalynn—who she shares with ex  Jeremy Calvert—entered middle school.

Backstreet's back to school! The former boybander posed with his and wife Lauren Kitt Carter's three kids Odin, Saoirse and Pearl, writing on Instagram Aug. 23, "Nothing better than watching your children grow and learn."

The HGTV host shared an emotional hug with her oldest son Drake—who she shares with husband Chip Gaines alongside their younger kids Ella, Duke, Emmie and Crew—as he headed back to Baylor University for his sophmore year.

The Buffy the Vampire Slayer alum showed off the back-to-school plaques she made for daughter Charlotte and son Rocky—both of whom she shares with husband Freddie Prinze Jr.—as they began high school and middle school, respectively.

Good luck, Mia! The actress—who played the titular toddler in Good Luck Charlie—started her sophomore year of high school on Aug. 19. 

She quipped on Instagram, "Cue the comments about feeling old."

Teenagers Braydon Wilkerson and Tucker Wilkerson—who the Sabrina the Teenage Witch actress shares with husband Mark Wilkerson—headed off to school on Aug. 7.

She got the boy to his class! The singer was on hand to watch her and ex Mike Caussin's son Jace start kindergarten on Aug. 9.

Meanwhile, the former couple's daughter Jolie began third grade.

The Bachelor Nation star's daughters Kinsley and Charlie started the seventh and fifth grade, respectively.

"I just can’t believe how grown up they are," she wrote on Instagram Aug. 22, "& that they still love to match…& that I still cry on the first day of school no matter how long I’ve been doing this."