Update 2 August 2019: Mr Archer was cleared of two counts of indecent assault.
A choirmaster gave reward stars to a pupil who he abused, a court has heard.
Kenneth Francis, 72, is accused of indecent assaults on four boys while he was a teacher at Widford Lodge Boarding School in Chelmsford in the 1970s.
One boy said he was abused beneath the school stage then rewarded with eight stars, Chelmsford Crown Court heard.
Mr Francis is on trial alongside 67-year-old Malcolm Archer, of North Wootton, Somerset, who denies two counts of indecent assault.
Mr Francis, of Pepys Court, Cambridge, has pleaded not guilty to 15 counts of indecent assault and two counts of gross indecency.
The allegations relate to boys who were members of the school choir between 1972 and 1979, the court heard.
Andrew Thompson, prosecuting, said Mr Francis had kissed pupils during one-to-one lessons before touching their genitals.
One boy said Mr Francis had got him to perform oral sex on him in an area beneath the school stage, the court heard.
Afterwards when the boy saw the teacher again he was given the reward stars which he told police were "for my performance under the stage".
Mr Thompson also told the court some of the boys had been abused by Mr Francis while away from the school.
One boy said Mr Francis told him "you will be sleeping with Malcolm" during an overnight stay, jurors were told.
That night the boy claimed he was sexually touched by Mr Archer, who played organ at the choir's concerts.
The trial continues.