A 15-year-old boy is in a critical condition after a stabbing at a school in south London.

Another boy, also 15, suffered knife wounds in the attack on the grounds of Kingsdale Foundation School, Dulwich at about 15:30 GMT.

Both are being treated in hospital, according to the London Ambulance Service.

A third teenager has been arrested and is being questioned at a south London police station, the Met said.

The stabbing took place at the school, where staff were having meetings with deputy head teacher Andrew Sear, on Thursday afternoon.

It is understood the school was not evacuated, however some students were kept inside until the situation was resolved.

An administrator at the school said he was being “flooded with calls” from worried parents.

He said parents had already been sent a text informing them of what had happened and he expected they would be updated later tonight.

The 18-year-old sister of one pupil, who did not want to be named, said: “It was in the atrium so a bunch of kids would have seen it.

“[My sister] was in the top of the English department but could hear screaming.”

Southwark Council said the school would re-open on Friday and students would be offered counselling.

At its last Ofsted inspection the school, which has 1,600 pupils aged 11-18, was rated as “good” with the behaviour and safety of the pupils considered “outstanding” by the education watchdog.

Following the incident, MP for Dulwich and West Norwood, Helen Hayes, tweeted: “Very distressing to hear of double stabbing of two young people in my constituency this afternoon – thoughts with the injured boys.”

The victims identities have not yet been publicized

In a separate incident, away from the school, former pupil Shaquan Mario Fearon, 17, was stabbed to death in September.