A headteacher has condemned colleagues for their "very misguided actions" in attending a party that led to a Covid-19 outbreak.
Eight members of staff at Holy Trinity Stacksteads CE Primary School in Bacup, Lancashire, contracted coronavirus following a gathering at the home of a former colleague.
Another three staff members, who did not attend the party, also later contracted Covid-19, forcing the school to close while pupils self-isolate.
Headteacher John Aspin explained the situation in a frank letter to parents, telling them the school's extensively planned safety procedures were not to blame.
He said that, earlier this week, he learned a "significant number of staff" had attended a "social event" on Saturday 5 September.
Mr Aspin added: "In doing so they were not breaking any of the lockdown rules in place at the time, but what they did do was jeopardise the hard work that had been put in creating bubbles within school, and numerous cleaning and organisational protocols, by mixing with each other.
"Had I been aware of the event I would have told them that they should not attend because of the risks, but sadly I was not informed.
"I have made my feelings of disappointment known to the staff who attended the event. I have also apologised to those of my colleagues who did not attend, especially to those who have now contracted the virus.
"I cannot defend the error of judgement that they made. They failed to appreciate the bigger picture of Covid-19 and, knowing each of them as I do, I know each will genuinely be regretting the decision to attend what last year would have been an enjoyable event but in the current situation was an ill-advised action to take, given their responsibilities to the children of the school and their colleagues.
"I offer sincere apologies for the upheaval and worry that you have to endure this week, and the disruption to your family and work lives.
"The school will recover from this trauma that has been inflicted on it by actions that were very misguided but not malicious, and will once again make Holy Trinity the wonderful place for your children to learn.