The teenagers would be back in court on June 18, as one of them has been admitted to Sterkfontein Psychiatric Hospital for mental observation, Warrant Officer Kay Makhubela said.
The other accused would also go for mental observation at Sterkfontein at a later stage, he said.
The boys, who cannot be named because they are minors, were arrested in connection with the murders of Thandeka Moganetsi, 15, and Chwayita Rathazayo, 16.
The girls were found dead in a field in Dobsonville in February. They were both in their George Khoza Secondary School uniforms when they were found with cuts on their hands and necks.
Three black candles and two new razor blades were found at the scene, leading to speculation that the murders were related to a satanic ritual.