Nathan Matthews, a Year 6 pupil at Stokenchurch primary school in Buckinghamshire, died during the last swimming lesson of the school term at Thame leisure centre, Oxfordshire, on Monday.
Nathan's father, Terry Matthews, 39, said: "I want the truth. I want the answers. I want to know if any neglect went into my son's death. If my son had been pulled out of the water immediately, would he be here now?
"Some children came round to the house last night who had been watching in the public gallery. They were shouting from the gallery. They realised there was a problem but could not be heard. It was one of the other children who was swimming that saw him."
A post-mortem examination on Wednesday found that Nathan had drowned.
Mr Matthews said Nathan was a "perfectly able" swimmer who had honed his skills in a pool in the family's back garden.
Andrew White, headteacher, said: "There were five relay teams swimming the width of the pool, with only five pupils in the pool at any one time. No one was diving and everyone was watched by fellow pupils, staff and the lifeguard at all times.
"Nathan was in 2ft 6 inches of water and appears to have got into difficulties when he went down for the relay ring. A fellow pupil very quickly noticed he did not surface and a member of school staff pulled Nathan out. Paramedics reached the scene within minutes."
A spokeswoman for Thame town council, which owns the swimming pool, said:
"Everything done was well within the emergency procedures."
Buckinghamshire county council has launched an internal inquiry.
Mr White announced Nathan's death to fellow Year 6 pupils on Tuesday. He said: "It was a heartbreaking message to have to deliver, and the whole school is in deep shock that such a young life could be taken so suddenly.
"The children have been invited to write down their thoughts and memories of Nathan as a way of helping them to grieve for him and work through the traumatic feelings this has caused."
Mr White was due to meet Nathan's parents this week to discuss how they would like the school to celebrate Nathan's life. He was one of a family of six.
An inquest into Nathan's death was due to be opened and adjourned today.
The police said investigations were continuing.