The Former Hear'Say signer, posted the picture to her Instagram page.
The caption read: "My big girl off to year 4!!! Time goes to fast!!! Have the best day my beauty."
Polly's dad, actor Jamie Lomas, wrote a series of heart-eyed and loveheart emojis and wrote: "Too much."
Another added: "Aww have a great day Polly."Recently Kym shared adorable photos of Polly cuddling her baby nephew Teddy.
My big girl off to year 4!!! Time goes to fast!!! Have the best day my beauty.Teddy is the son of Kym's eldest daughter Emilie and her boyfriend Mike Hoszowsky.
Kym has son Dave and daughter Emilie from her relationship with Dave Cunliffe.
Polly is Kym and Jamie's daughter. Jamie and Kym also had a son named Archie who was born 18 weeks prematurely and sadly passed away.
Earlier this year, Emilie announced she was expecting her first child with boyfriend Mikey.
The couple gave Teddy the middle name Archie in honour of Kym and Jamie's baby son.
Back in February Kym announced she had quit Coronation Street after 13 years.
She told The Sun newspaper: "When I was lucky enough to be offered four episodes I could never in my wildest dreams have thought I'd be here 13 years later.
"It's been an incredibly difficult decision but it feels like the right time for me to explore some other roles."
Kym's departure from the show was confirmed by Corrie executive producer John Whiston, who said he was "sad" to be losing her from the show, but "totally understands" her desire to head off into new ventures.
He said: "Kym has done a fantastic job. She has brought incredible heart and humanity to some hugely important stories.
"We will be really sad to lose her when she goes but totally understand that, after dedicating herself to the show for so long she now fancies trying something else."