A serial bike thief has targeted Christchurch Boy's High School, stealing five bikes from six visits. CCTV footage shows the thefts.

Police are hunting for a serial bike thief plaguing a Christchurch school.

The thief has struck Christchurch Boys' High six times, stealing five bikes in the past 12 weeks.

Supplied The same man walks into the grounds at Christchurch Boys' High School.

School senior master Craig Dunnett said the bikes were stolen during the day.

Many of the thefts were committed by a man who rode into the school through the Kahu Rd entrance wearing a silver helmet with a baseball cap underneath.

On one occasion, the man wore a hi-vis vest, Dunnett said.

Supplied An alleged bike thief in the grounds at Christchurch Boys' High School.

"He bikes in [to the school's bike shed] and leaves his bike there and bikes out on one of the students' bikes."

The man then returned a short time later to collect the bike he arrived on, Dunnett said.

"The students come to me at the end of the day extremely upset," he said.

One of the boys had to catch three buses to get home to Sumner after his bike was stolen.

The most recent theft was at 1pm Monday.

"He's a serial bike thief, definitely."

Dunnett said the school had two security cameras monitoring the bike shed, which could only be accessed by riding through the school grounds. A more public access was locked.

Footage of Monday's incident was being passed to police on Tuesday night.

Detective Senior Sergeant Scott Anderson said police had received two complaints about bike thefts at Christchurch Boys' High School this year.

Further information about other thefts was being collated with Dunnett's help, Anderson said.

Glenn Kruger's 13-year-old son, Charlie, had his $1400 bike stolen from the school grounds on Friday, May 8. Charlie Kruger saved money to buy the bike in January.

"He is pretty unhappy and down about it," Glenn Kruger said.

"I am frustrated. I would like to try and identify the people involved. We would like to get our bike back but I don't think the chances of that are very high."

Anyone with information about the bike thefts should contact Christchurch police on (03) 3637400 or Crimestoppers anonymously on 0800 555111