All Saints Primary School acting headteacher Jacqui Kearney said: “This morning was the first time we have used the pool this summer, and unfortunately four children reacted to chemicals in the water.
“We acted promptly to ensure their safety and well-being. Four children were taken to hospital as a precautionary measure and three of them have since been discharged. All other children appear to be unaffected.
“The swimming pool is now closed and it will be inspected tomorrow to establish what caused today’s issue.
"We are writing to parents today to inform them and remind them, as always, the safety and well- being of all the children at our school is our highest priority.”
More top news
A number of teenagers, aged 13 to 15, from Portsmouth, have been treated in hospital, after taking tablets believed to be diazepam.
Thursday Evening's Pollen Forecast
Thursday night's weather for the east of the region