Four pupils were taken to hospital over fears they had taken cocaine at their Dorset school, mistaking the class A drug for sweets.
Emergency services were called to Broadstone middle school in Poole and the children were checked at the site by paramedics before being taken to hospital, where they underwent further examination.
A spokesman for Dorset police said officers were called after reports that four pupils had taken a white powder brought in by one of the pupils.
He said: “The children believed the substance was sweets, but it has now been established it was cocaine. While it was not believed any of the children ingested the powder, they were taken to hospital to be checked over. They were assessed to be in good health by medical staff and were discharged.
“A 32-year-old Bournemouth man has been arrested on suspicion of drug offences and is currently on police bail until the middle of February pending further inquiries.”
The incident took place on 3 January, the first day of school after the Christmas holidays.
A spokeswoman for South Western ambulance service said: “We were called to Broadstone middle school following reports that four pupils had come into contact with an unknown substance. They were treated at the scene before being taken to Poole general hospital to be checked over.”
It is not known how old the children were but the school has pupils aged nine to 13.
The headteacher, Dawn Wilks, told the Bournemouth Echo: “We can confirm that a child was found in possession of what was believed to be a drug. The children believed the substance to be sweets.
“The police were immediately called and four children taken to hospital to be checked over. They were not found to have any health issues and were discharged the same day.
“We would like to reassure parents that this incident was dealt with swiftly and in line with our policies. Police inquiries are ongoing regarding this incident and as such we are unable to comment further at this time.”