John Parker, the director of Rainsbrook Secure Training Centre, told the inquest into the death of Gareth Myatt that he has not read the Physical Control in Care manual, and was not aware of the risks involved.
Gareth, 15, died after being restrained at Rainsbrook in April 2004. Parker has been in post since 2001.
The inquest, which started last week, has also heard from Gareth's mother, Pam Wilton, and Mark Perfect, who was chief executive of the Youth Justice Board at the time of the tragedy.
Perfect said he was ashamed that more had not been done.
Deborah Coles, co-director of bereavement charity Inquest, said: "The evidence that is coming out is even more shocking than I could have imagined."