A 12-YEAR-OLD boy arrested after 21 pupils were taken ill when a substance believed to be pepper spray was released at their school has been bailed.

The boy, who was held on suspicion of possessing a banned weapon and discharging a noxious substance, was freed on bail shortly before 9pm last night.

The 1,200-pupil Christ Church High School in Ashford, Kent, was evacuated after the substance was let off in the rear stairwell of a classroom block at about 12.20pm yesterday.

Twenty-one pupils were taken to the William Harvey Hospital suffering from minor breathing difficulties, coughing, sore eyes and vomiting, and all were later sent home.

Ambulance crews assessed a further 35 pupils at the scene while fire crews wearing breathing apparatus ventilated the building.

In a separate incident, two parents were arrested at the school on suspicion of assaulting police and were taken into custody at Ashford police station.

A Kent Police spokesman said the two men, aged 32 and 37, have since been freed on bail pending further inquiries.

Police said officers used parva spray during the arrests of the pair - an entirely different substance from the illegal one that was used inside the school.

Lessons returned to normal a couple of hours after the incident, a Kent County Council spokeswoman said.