A teenage girl has been airlifted to hospital after suffering stab wounds in an incident outside a secondary school, police said.
West Midlands Police arrested an 18-year-old man at the scene of the incident, which happened near Ridgewood High School in the Wollaston area of Stourbridge.
Initial indications suggest that the victim, who is believed to be about 15, has been seriously injured, a police spokesman said.
The police spokesman said: "Officers received an emergency call at 8.42am today (Friday) after a girl had sustained injuries, believed to be stab wounds, outside Ridgewood High School, on Park Road West.
"The girl has been airlifted to hospital for treatment. The girl's family have been informed and are en route to hospital."
The man who was arrested was detained by witnesses at the scene and was arrested when police arrived shortly afterwards.
Chief Inspector Mark Bramwell, from Dudley Police, said: "We are in the very early stages of this inquiry. However, we do believe this to be an isolated incident and wish to reassure other pupils and parents that there not any known risks to any other individuals.
"Local officers and detectives will be at the scene today to speak to those with concerns, or information they wish to pass on to the investigation team.
"A man is currently in police custody and will be questioned in due course."