"I was a little surprised with the best actress and supporting actress, just based on what the critics had said," said Johnston, 18, a freshman at Hood College in Frederick, Md. Johnston had picked Christie and Blanchett to win.
"There's always a few surprises at the Oscars. That's what makes it interesting," she said.
In making her picks, Johnston said she primarily went with the critics' choices, and then with her gut.
"I haven't seen a lot of the movies, but I'd really like to see them," Johnston said.
However her winnings won't be going toward box office tickets.
Johnston said she plans to put the money in her savings account for college. She's studying English and considering a career as a high school teacher.
During her junior year at North Hagerstown High School, Johnston wrote for The Herald-Mail's Pulse section, the teen section that runs on Tuesdays, and was an intern at the newspaper during her senior year.
Other contest entrants who guessed eight of the 10 categories correctly were Mike Price of Fayetteville, Pa., and Hagerstown-area residents Paula Hurbanis Leaf and Janet Dame.
Oscar winners in the 10 contest categories
1. Best Picture: "No Country for Old Men"
2. Director: Joel Coen and Ethan Coen, "No Country for Old Men"
3. Actor: Daniel Day-Lewis, "There Will Be Blood"
4. Actress: Marion Cotillard, "La Vie en Rose"
5. Supporting Actor: Javier Bardem, "No Country for Old Men"
6. Supporting Actress: Tilda Swinton, "Michael Clayton"
7. Adapted Screenplay: Joel Coen and Ethan Coen, "No Country for Old Men"
8. Original Screenplay: Diablo Cody, "Juno"
9. Animated Feature Film: "Ratatouille"
10. Foreign Language Film: "The Counterfeiters," Austria