Agnes Zhelesnik, or Granny, as her students affectionately call her, turned 99 years old.
The school held a special celebration in her honor.
And if you need proof that it's never too late in life to try something new, Granny didn't begin teaching until she was in her 80s.
She is widely regarded as the oldest working teacher in America, teaching prop building and costume making at the Sundance School.
Hundreds attended the celebration, including many of her former students. They presented her with a quilt, a cake and 99 red balloons.
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