A father has died after he was allegedly attacked in front of hundreds of children outside a primary school during afternoon pick-up. 

The 63-year-old was allegedly assaulted at a reserve at the back of Strathaird Primary School in Narre Warren South, south-east Melbourne, at 3.15pm last Friday.

The man's son attends the school and reportedly witnessed as two men allegedly beat his father with their fists and a pole or metal torch. 

All three men are understood to have known each other. 

The 63-year-old man was taken to hospital before he died on Thursday.

One parent told the Herald Sun that children had witnessed the alleged assault, with about 760 students enrolled at the school.

'The kids were shaken up,' she said.

'They were terrified. I could see him lying on the ground and he couldn't get up. He appeared to be knocked out.

'I believe his child was there when it happened.'

School parent David Wade said he had already picked up his son Liam, 9, when he saw the 63-year-old man lying bloodied on the ground.

'He was very incoherent. He had blood on the back of his head. I made sure everyone was calling the police and ambulance,' he said.

'He said he felt dizzy and like vomiting. Poor old bloke.'

Strathaird Primary School has offered wellbeing support to children and staff.

A Department of Education spokesman said the safety and wellbeing 'of students and staff is always our priority'.

'Those who witnessed the incident have been offered wellbeing support and the school is working closely with families,' he said.

Liam Robert Hartnett, 22, and a 21-year-old man were charged with recklessly causing injury prior to the 63-year-old man's death on Thursday. 

Police said 'alternate charges' would be considered following a post-mortem.