However, she learned from the experience and went on to win two world championship events in 2009.
Ms Walker, aged 23, lined up 25 students side by side on the stage to demonstrate the length of the jumps she does during her races.
"There are times when I don't want to do it," she said.
"There are times when I'm so scared that I want to cry, but I still go up there and do that jump."
Falling off her bike could be discouraging, Ms Walker said, but mistakes were good opportunities to learn.
"If you think about processes and learn from your mistakes, next time you'll be much better," she said.
Lauryn Smith, 10, of Glenbervie School, said she liked Sarah Walker's presentation because she had been encouraged to step up and do the things that she didn't want to do.
"She said that she's been a bit nervous about some of her races but you can definitely overcome it."
Lauryn's classmate Toby Clayton said he liked listening to speaker Marcus Akuhata-Brown.
Toby said Mr Akuhata-Brown had overcome a number of obstacles and had gone on to achieve great things.
Originally from the East Coast of the North Island, Mr Akuhata-Brown said he had not been encouraged early on in his life to make the most of life.
However, with the encouragement of a helpful teacher, he had attended university and gone on to travel the world as a diplomat and international representative.
"When I was young I was thinking school isn't for me and I just wanted to cruise," Mr Akuhata-Brown said.
Making good decisions at critical times is important, he said.
"Take opportunities, make good decisions, have good friendships, listen to people who have your best interests at heart."
