Governors and council officials have spent the weekend arranging alternative teaching facilities for more than 100 pupils after the fire on Thursday night.
Police believe that a group of children set fire to a bin and the flames quickly spread out of control, leaving the school a blackened shell.
Two local boys, aged ten and 11, were arrested shortly after the fire began. They have been released on bail pending further investigation.
Emergency services were called to the school in Pinewood Park at around 6.45pm.
At the height of the blaze, 11 engines and 65 firefighters were battling against the flames.
Hampshire Fire and Rescue has denied reports that several firemen were injured, saying that one crew member sustained a sprained ankle.
Caroline Whitcombe, whose son goes to the school, became aware of the fire when her children ran into the house.
She said: “My son and some friends had been in the park next to the school and they came back at about 6.45pm to tell me that the school was on fire.
“They said that it was only some bins but then when we went out there it just got bigger and bigger. Then the glass shattered and it got out of control.”
Roy Jordan’s house backs on to the school and he saw events unfold from a bedroom window.
“It seemed to go on for a long time. I was surprised that after a period the firemen seemed to back away from the school, as if they thought there was nothing else they could do.
“There were lots of people watching from everywhere. I said to my wife ‘at least there were no children in the school when it happened’.”
The fire was brought under control at around 1am and crews spent the night damping down any hotspots.
As bewildered teachers and parents arrived at the school on Friday morning the full extent of the damage was clear to see.
Chairman of governors Mildred Stock described the scene as “horrific”.
“I was down here last night when it was ablaze. The real tragedy is that staff have worked really hard to improve things and they had got everything up and running.
“The important thing at this time is keeping the staff together and keeping morale up.”
The school was home to a specialist language unit used by children with speaking difficulties from several schools.
Fernhill ward councillor Alan Ferrier was governor of Pinewood Infants from 1986-2000, and he was at the school on Friday to lend his support to parents.
He said: “I was visiting a resident on the estate last night and I heard someone say that the school was on fire.
“I have already been in contact with the county councillor responsible for education, Don Allen, to see what can be done about teaching arrangements.”
One angry father, who did not want to be named, blamed the council for failing to clamp down on unruly behaviour on the estate.
“The school has regularly been the target of vandals. They have attacked the play area and broken windows.
“I don’t think that the fire was malicious. I expect they were just messing around. But now the kids have been left without a school and their work has gone up in flames.”
Hampshire County Council education officer Chris Holt said it was unlikely the pupils would go back to school until the start of the summer term.
He said: “Our key priority now is to try and ensure the pupils from Pinewood Infant School are able to resume their schooling as soon as possible.
“The fire has caused considerable damage, destroying about 80% of the school and leaving the remaining 20% unusable.
“County Council and school staff are working together to find alternative accommodation for pupils, and would generally provide a temporary school on the existing site, although due to space limitations we are having to explore other options.
“Our aim now is to set up the school in temporary buildings on a site — which still needs to be determined — but it is unlikely that pupils will be resuming their schooling until after Easter.”