She said she was proud of her achievement.
Grace estimated spending four to six hours a day answering questions for the competition.
"But it was worth it. It helped me remember things. It's a cool language and fun to learn."
Students who achieve 10,000 points or more are given an elite award. Grace earned almost double that with 19,530 points.
Liam Winn, 17, came 28th in the world in the category after putting in about 20 hours during the 10-day competition.
"I was very proud, it was a huge accomplishment, I know how many people participated and it was a big improvement on where I started," he said.
"Spanish is very useful as a global language. When I first started learning it I was in a region in America where it was commonly spoken so it was important. It's fun to learn and there are lots of opportunities to use it."
Western Heights High School Spanish teacher Lois Parker said she was proud of the participants.
"We're batting way above our average. The kids worked so hard," she said.
"To get to the position these kids are at, you have to be the top 0.4 per cent in the world."
The school as a whole placed second in Spanish across all countries, with 227,003 points. It was first in its category which was 101-250 students.
"I tell them I'm a proud profe [teacher]," Parker said.
"For me one of the greatest achievements is kids who don't excel in many things but they plug away and learn."
