OXON HILL, Md. (AP) — The 90th Scripps National Spelling Bee promises to be more difficult than any of the 89 bees that preceded it.

The bee got underway Tuesday morning when 291 well-read elementary- and middle-schoolers gathered at a convention center outside Washington to take a written test. The nerve-wracking exam goes a long way toward determining who will be among the 50 or so spellers to advance past Wednesday's preliminary rounds.

Last year, the bee extended the final rounds and made the championship words tougher in an attempt to avoid a third straight tie. But two spellers still ended up sharing the title. This year, the top spellers will take another written test that will be used as a tiebreaker if necessary.