A student who was excluded from school is being questioned by police after a stabbing at a school site that left one teenager in a critical condition and another with minor injuries.
The two victims, both aged 15, were attacked at the Kingsdale Foundation School in Dulwich, south London, just before 3.30pm today.
The school sent information to concerned parents as senior staff held urgent meetings.
In a statement, the Metropolitan Police said: "One teenager remains in a critical condition. The other boy is in a stable condition."
Both were taken to a south London hospital, however headteacher Steve Morrison later confirmed the teenager with the less severe injuries had been released.
He said: "We've been informed that a 16-year-old is assisting the police with their enquiries."
Mr Morrison added: "We are fully collaborating with the police and are not at liberty to comment further or speculate over the source of any misinformation released into the public domain."
Contrary to earlier reports, an air ambulance was not involved in the response and the school was not evacuated.
Some students were held inside while emergency services responded to the situation.
Mr Morrison confirmed a student who was excluded from the school site was involved.
He said: "The school is open tomorrow, the police have informed us there is no reason it shouldn't be open.
"At this stage I understand they are satisfied they have the suspect they wish to talk to."
Mr Morrison said parents would be emailed an update on the incident on Thursday evening.
A Southwark Council spokeswoman said: "We are assisting with the police investigation in any way that we can."
Police spent a number of hours speaking with staff inside, while teachers who left the premises would not comment on the matter.
Residents of the nearby estate said they know nothing about the stabbings.
Alleyn Park, the road which the school lies on, is part of a leafy suburban area of the borough of Southwark.
Detached houses face the school, which is a few minutes' walk from the prestigious Dulwich College.
Many of the students at Kingsdale come from the nearby Kingsdale Estate.