The Star building, on Greenfoot Lane, was shut to its pupils earlier this week after cleaning staff noticed shards of glass in corridors.
A letter sent to parents, and seen by the Chronicle, shows the vandals even used the netball post to help smash two windows in a year two classroom.
It said: “The alarm had not activated as the culprits had not actually entered the building, thus the motion sensors had not been triggered.
“In total 12 windows have been smashed, to varying degrees.
“Some of these windows have been attacked to the extent that shards of glass are in the school.
“One broken so much that the brick was lying in the corridor.
“Those involved have also trashed the playground and even used the netball post to help smash two windows in a year two classroom.”
Headteacher Dean Tombling admitted he didn’t want to close the school - especially due to the lack of face-to-face learning since the pandemic began - but felt he had no other choice.
“Closing a school is something I have always been loath to do, but even more so after the last two years,” the letter added. “However there was no way that the building could have been made safe for the children for the start of the day, due to glass in the cloakrooms and toilets, plus the shattered glass that the children could touch.
“The earliest the glazers can get to us is at midday today, and with the need to secure 12 windows, the building opening today was not possible.”
Mr Tombling has admitted the school may look different for kids when they return.
”Finally for those of you that offered to help, thank you so much, it is greatly appreciated, but we have everything organised.
“If you do have any information about who may have caused this damage to our school, I would more than gladly pass that information onto the police.”
Barnsley North’s Neighbourhood Policing Team are encouraging residents who have any information to come forward.
“The team are extremely saddened to hear of the mindless vandalism to windows at Wilthorpe Primary School over the weekend,” a spokesperson said.
“This has meant the school has had to close for the day and we understand the disruption and concern this will cause.
“Do you live in the vicinity and see this happening?
“Do you have CCTV or dash-cam that could assist us?
“If the answer is yes, please get in touch via 101 or online and quote investigation 14/64587/22.”