Once upon a Saturday morning three little girls found themselves prisoners in a boarding school ruled by Mrs. Brown, a fiendish teacher and wicked witch. There was only one way out.

"Make her eat liver," suggested one spirit in the school who had been made captive by Mrs. Brown's evil spell."Everybody knows when witches eat liver they lose their powers for 24 hours."

Fourteen-year-old Allison Hopper, off to a running start with her writing career, sometimes puts off pressing assignments so she can devote more time to what she loves best. "I'm always writing and I never do my homework," said Hopper in a radio interview the other Saturday before her 1979 prize-winning play was broadcast. The play, "The Haunted Schoolhouse," written when Hopper was 12, may not make it to Broadway, but it was selected by Children's Radio Theater as one of several winners in the first annual Henny Penny Playwriting contest for children six to 17.

The story and the audience are part of a children's program aired on WPFW (89.3 FM) on the last Saturday of every of every month. The program has won the Peabody award for excellence in broadcasting and the Ohio State educational program award for three consecutive years.

Children Radio Theater was the brainstorm of Doris Indyke and Joan Bellsey, who met during the first production of Henny Penny at WPFW in 1977.

For the children, this is their first exposure to bright lights and stardom.

"They get real turned on to listen to their voices on the radio," said Indyke. "We introduce kids to a lot of different art forms all at once." After their first exposure the children sold, said Indyke: "They start making their own radio shows at home with tape recorders."

Parents are encouraged to call in with thoughts and impressions.One discriminating nine-year-old called in the critique "The Haunted Schoolhouse." "If I wrote the play," said the budding author, "I wouldn't have done nothing different."