A teenage boy has been arrested in connection with the fight at Grimsta school in Upplands Väsby in northern Stockholm, with police conducting a search for suspected accomplices.
The teenage victim who was injured in the fight was rushed to Karolinska Hospital after sustaining stab wounds in the fight on Tuesday morning.
"The person was conscious when ambulance staff arrived," said Ulf Lindgren at Stockholm police.
Stockholm police have described the victim's condition as "stable" while his injuries had previously been described as "life-threatening".
Police are searching for five other teenage boys who are suspected of having come to the school on Tuesday morning.
Witnesses have testified to how the gang attacked and stabbed the teenage student and police believe that he was targeted deliberately.
Police have classified the case as attempted murder.