Thirteen-year-old champion ice skater Sarah Hughes, daughter of John and Amy Hughes, will represent the United States at the Qualified World Championship event in Helsinki starting on March 19.

The event is usually limited to those at least 15 years old, but Ms. Hughes was granted an exception because she was medaled in the Croatian event last year.

Ms. Hughes has a busy schedule planned for March. She is due in Detroit on March 10 to compete in the Grand Prix finals there. ''I will be the only girl in my competition from the United States,'' she said.

The fourth of six children, Ms. Hughes is not the only one of her siblings to keep her parents hopping. Emily, her younger sister, will participate in the Junior Olympics in Pittsburgh, also in March. The oldest Hughes, Rebecca, will graduate from Harvard, where she is majoring in government, this coming June.

''I still can't believe that Sarah will be competing in the World Championship,'' said her mother. ''I know she's good, but she's only 13!'' Mrs. Hughes credits her daughter's teachers for making it possible for the young skater to keep up with her grueling schedule. ''The faculty of North Middle School has been so cooperative and understanding,'' she said. ''They see that Sarah keeps up with the work she misses while she is away at competitions. And her guidance counselor, Suzanne Spinrad, has helped her coordinate her activities. We can't thank her enough.''

Ms. Hughes got her start in skating at the Parkwood Ice Skating Rink at age four. She attended classes at the Parkwood skating school on five levels, and still practices there many mornings a week. She has been in many of the Parkwood shows. ''Sarah is an inspiration to many young skaters of Great Neck,'' said Richard Arenella, Superintendent of Parks. ''She is someone for them to emulate, for her dedication and skill.''