King's head boy Caleb Gray (17) said the money was raised through the school's annual raffle, and was destined to be injected back into the school.
However, the Christchurch earthquake in February left "their brothers" without a school. The 1350-pupil premises was left uninhabitable.
Until the school can be rebuilt, the Shirley boys will share classrooms with pupils at Papanui High School.
"Shirley Boys is our brother school. We do sporting and cultural exchanges with them all the time," Caleb said.
"So, the school council thought it would be a nice idea to support our friends in Christchurch and show we are here for them."
Caleb said the raffle usually raised about $10,000 for the school each year.
"But the [King's] boys put a lot of effort into selling them and the community was very generous with their response."
Caleb said he had heard Shirley Boys' was one of the worst-affected schools in Christchurch and it could be a couple of years before rebuilding was completed.
"Hopefully, this money will go a small way towards helping them back on their feet again."
