A 21-year-old man who sprayed a crowd with gunfire following a basketball game at a Catholic high school in Brooklyn will serve eight years in prison after pleading guilty yesterday to gun possession.

Keenen Upson has been locked up since his arrest in January 2011, after he fired a 9 mm semiautomatic into the crowd outside Bishop Loughlin HS.

He wounded five teenagers.

“You’re still going to be a young man when you get out,” Justice Patricia DiMango told Upson. “You better smarten up and do something with your life.”

If convicted at trial, Upson faced up to 25 years.