ATLANTA (AP) _ Parents and students at Chattahoochee Elementary School knew that a child there had AIDS. They didn't know who. So third-grader Brett Lykins decided to tell them.

''It was my turn to go up'' for show-and-tell on Friday, he said afterward in a soft, unwavering voice. ''I just went up and said I was the one. It's been hard to keep this secret. I decided not to keep it anymore.''

Brett's identity had been kept secret from all except the principal and his teacher, in accordance with the Gwinnett County school system's 2-year-old AIDS policy.

''I think the kids in class felt really happy that I did this,'' he said. ''I think some of them knew I had it, but there were some who didn't.''

One classmate told Brett, 9, she would pray for him every night, said his mother, Marty Lykins, who accompanied her son to school after he told her of his plans to reveal his secret.

Another friend gave him a wind-up doll. ''She said she wanted me to have it. But that's not why I did this. I don't want them to give me a lot of stuff. I just want them to know.''

After show-and-tell last week, Brett's teacher, Nancy Terry, led the class in a health lesson that focused on AIDS, which destroys the body's defenses against disease, leaving a person prey to life-threatening infections and certain cancers.

Brett's father, Steve Lykins, said his son's health has been relatively good despite the AIDS infection, which was contracted from a blood transfusion received shortly after his premature birth. His parents learned in 1987 that he had the disease, and Brett was told this year.

Health experts say Brett's presence in class does not endanger his classmates.

Ms. Terry said Brett's show-and-tell session ''was a wonderful experience. ... The children have been so nice.''