High Note in Prague for the Children's Aid Society Chorus

The Sullivan Street home of the Children's Aid Society Chorus has a new bauble: a shiny silver trophy representing the chorus's recent second-place finish in the Prague International Choir Festival and Competition.

It was the first taste of competition for the chorus, which competed against contenders who had taken top honors at other contests. ''No one thought we were a threat,'' said Francisco Nunez, who directs the 44-member Children's Aid Society Chorus. They range in age from 12 to 18 and come from all sections of the city. Most are on scholarship and represent a mix of cultures: Hispanic and black, Muslim and Christian.

''They asked us what we knew about the other choirs,'' Mr. Nunez said. ''But we made it happen as any homogeneous group could.''

The chorus shared second place with a women's choir from an Atlanta suburb. A boys' choir from Fort Lauderdale, Fla., finished first.

Next month, Mr. Nunez said, he plans to start another children's choir, to be called the Young People's Chorus and housed at the 92d Street Y.

In Prague, the children visited tourist sites and practiced Brahms's ''Ave Maria'' and an Inuit piece while riding the bus and after returning to their rooms late at night. Their attitude, said Mr. Nunez, was: ''We're here to win. We've never lost.''

Jaclyn Rochez, 16, said that when they found out they had placed in the competition, ''I think we woke everyone up in the building.'' She added: ''We were on TV. We couldn't come home empty-handed.'' Instead they returned with the trophy and about $500 in prize money.

When their second-place finish was announced, every child called home, Mr. Nunez said, adding, ''I don't want to see the credit card bill.'' KAREN HSU