Teacher creates $20 kindness challenge in memory of her sister. Photo: abc7ny.com

In 2014, Kristina Ulmer's younger sister Katie Amodei 29, a waitress known for her kindness, died suddenly in an auto-accident in northeast Philadelphia.

Kristina collected her sister's purse, containing over $100 in tips.

"Katie was such a kind person, and I remember thinking, 'This money should go toward kindness,'" Kristina, now 42 told The Washington Post.

"I put the purse in a cabinet in my living room, and for a long time, I wondered what I could do with that money in Katie's memory."

Four years later, Kristina, a 9th grade high school English teacher, had a marvelous idea:

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What if she gave each of her students a $20 bill and asked them to do something kind with it, and then record that act of kindness to share with others.

Teacher gives $20 to her students with one rule. Photo: abc7ny.com

She called it the "$20 Kindness Challenge." Adding her own money to Katie's tips, she gave $20 to each of her 25 students, totaling $500.

They did great things and Kristina has continued her $20 Kindness Challenge. Examples of what these students then and now have done with the money:

Sydney Cassel, left, and Mackenzie Bombas made treats for teachers at their high school. Photo: washingtonpost.com

One girl bought yarn and knitted tiny red caps for babies with heart issues so they could be easily spotted in the NICU. Others bought hygiene products and food for the homeless.

Two girls went to Walmart, combined their money, and bought Legos for a very happy little boy. Three girls combined their money and made dog blankets for a local animal shelter.

There are so many great stories! Watch some of the students describe their acts of kindness below.