“I knew Kayleigh really needed it, so I thought, ‘Why not try?’” Kayleigh Kulage’s pre-school teacher, Robin Mach, tells PEOPLE ahead of Teacher Appreciation Week
Kayleigh Kulage
Credit: Desiree Kulage

From the time she was born, 5-year-old Kayleigh Kulage's life has been filled with surgeries, dialysis and doctor's appointments. 

The Pacific, Missouri pre-schooler was born premature at 26 weeks and, after spending more than 150 days in a neonatal intensive care unit (NICU), was diagnosed with partial blindness, a compromised immune system and failing kidneys that have required 11 hours of dialysis treatment every day, among other health issues. 

Kayleigh's parents Josh and Desiree Kulage were desperate to find their daughter a new kidney — and when she finally reached the minimum height and weight requirements to receive a transplant in October, a possible donor came from the most unexpected place: Kayleigh's classroom. 

Kayleigh and parents
Kayleigh smiles with her parents Josh and Desiree
| Credit: Desiree Kulage

Robin Mach, an early childhood special education teacher, had been teaching Kayleigh for more than two years. When she found out Kayleigh needed a kidney transplant, she "didn't think twice" about offering up her organ, Mach tells PEOPLE ahead of Teacher Appreciation Week, which begins Monday.

"I just asked Desiree one day, because I knew Kayleigh really needed it, so I thought, 'Why not try?'" Mach, 46, says.

Mach describes Kayleigh as a "spunky, energetic" child, adding, "It's really fun being her teacher."

One of the challenges Kayleigh faced in receiving a transplant was finding a kidney small enough for her body, as she is small for her age, weighing in at 26 lbs. and standing at about 2 feet, 10 inches tall, according to her mother, Desiree. 

Mach, meanwhile, is under 5 feet tall. After roughly three months of tests and what Kulage calls "a rollercoaster of emotions," doctors approved the teacher to be Kayleigh's donor. 

"I was so relieved and excited when I found out because Kayleigh's kidney was coming from someone we knew," Kulage, 34, tells PEOPLE. 

In February, Kayleigh and Mach underwent a successful six-hour kidney transplant at joint hospitals in St. Louis. Robin had her surgery first at Saint Louis University Hospital to remove the kidney, which was then rushed to Kayleigh at Cardinal Glennon Children's Hospital via underground tunnel. 

Robin Mach
Robin Mach before her transplant surgery
| Credit: Robin Mach

Kulage says Kayleigh has recovered well from the surgery and was "moving and grooving to go" as soon as she woke up.

"She's an extremely resilient kid — she likes to point to her scar and show off her new kidney," she adds.

Though she doesn't yet understand that her new kidney came from "Miss Robin," Kulage adds that Mach is one of Kayleigh's favorite people.

"She sees her as her playtime buddy," she says. 

Mach felt sore for a few weeks following the surgery but stresses that it was a simple recovery.

"I don't think people realize how easy it is to donate [an organ], so I hope by sharing our story, more people will think about doing it," she notes. 

Robin Mach
Robin Mach was recognized as a "Building Teacher of the Year" by the Meramec Valley R-III School District in Missouri
| Credit: Robin Mach

Kayleigh's health has drastically improved following the surgery, according to Kulage. She's not tethered to her dialysis machine every night, the color is returning to her cheeks and she can now take long baths before bed. The Kulages are even planning their first family vacation. 

Kulage says she'll "never find the right words" to thank Mach.

"Donating a kidney really is remarkable, it saves people's lives and gives them a better quality of life," she adds. 

The Pacific, Missouri community has rallied around them throughout the transplant process. The Doris Hoffman Early Childhood Center, where Mach works, raised money to help the Kulages pay their medical bills and designed t-shirts with Mach and Kayleigh's names on it to show support. 

As for Mach, she doesn't consider her actions heroic — just part of her job as a teacher.

"If a kid needs a backpack or shoes at school, I get them the backpack or shoes," she says. "It's kind of the same thing … Kayleigh needed a kidney, and whatever she needs, I'm going to give it to her."