The condition is now better for the 15-year-old boy who was shot at Trångsundsskolan in Huddinge, reports P4 Stockholm.
The school's principal Kaj Majuri tells the radio that the boy has been operated on and will not suffer any permanent damage from the incident.
The shooting occurred inside the school just before 8:30 am on Wednesday. It took place in a confined space where no one else was present except those involved.
A 15-year-old boy was arrested on Wednesday, suspected of attempted murder and serious weapons offenses.