Franklin Regional High School sophomore Greg Keener was released from Forbes Hospital around 2 p.m., hospital spokesman Jesse Miller said.
The 15-year-old was one of 20 students wounded when authorities say a classmate wielding two kitchen knives rampaged through the suburban Pittsburgh school on April 9. A security guard was also wounded.
The hospital said Keener's family asked for privacy as he continues to heal.
"An emotional attachment exists throughout the hospital for these young men and their families and there is tremendous joy knowing that they all survived," said hospital CEO Reese Jackson.
Alex Hribal, 16, has been charged as an adult with 21 counts of attempted homicide and aggravated assault. He is scheduled for a June 4 preliminary hearing.
Defense attorney Patrick Thomassey has acknowledged Hribal stabbed the victims and is seeking to have his case transferred to juvenile court, where he would only face incarceration until age 21.
Thomassey has argued that Hribal's mental state should be considered in determining whether he be tried as a juvenile or in the boy's defense if he is tried as an adult.