Outwood Academy: Dozens fall ill at school in Ripon, Yorkshire
11 November 2015 Last updated at 18:54 GMT
Up to 40 pupils have simultaneously fallen ill at Outwood Academy in Ripon.
North Yorkshire Police said they had "displayed signs of sickness and feeling faint sometime between 11:00 and 11:30".
A fire officer told the BBC they believed the hall "was a hot room and some children had become overwhelmed" but that no chemicals or gases had been detected in the scare.
BBC Look North's Danny Carpenter reports.