HERNE Junior School closed for two days after fears its water supply had become contaminated.
Concerns about the quality of the water were raised early on Monday morning.
The education authority, Hampshire County Council, immediately closed the school in Love Lane, Petersfield, and sent its 460 pupils and 67 staff members home.
The council also called in experts to take water samples for testing.
Headteacher Tony Markham said: “The water had a slightly slimey feel and an odour, and water board experts agreed with us about that, and there was no option but to close the school.”
But after two days of chemical, organic and biological tests, the water was declared to be fine.
And further tests carried out on water from residents’ homes in nearby Love Lane also came back all clear.
Mr Markham said: “We will reopen today (Wednesday) as normal.
“During the two days, the school was the emptiest I have ever known it to be. There was just a skeleton team in, about three of us.
“Even during the holidays, there’s normally more people about.”
Within minutes of getting the all-clear, the news was posted on the school website – Herne is back to normal.
But the short notice closure has revealed another unexpected issue.
Mr Markham said: “Like all schools we have emergency plans in place.
“One of the things we are meant to be able to do is group text all the parents in the event of an emergency, or if we have to send the children home unexpectedly.
“We used the group text system to ask all the parents to collect their children.
“It was only later when a few parents arrived saying that they only learned about the school shutting by chance from friends, or by visiting our website, we realised there was a problem.
“It seems if a parent has a poor signal, the text service will only try twice to deliver the text before giving up, which could cause issues.
“I will be taking this up with the service provider because at times we may unexpectedly need to contact all the parents, as this has shown.”