Trespassing is the number one cause of deaths on the rail network in New Zealand. More than 148 people have died trespassing on railway tracks since 2000.
The Northern Advocate understands one Boys' High student has been disciplined for "train surfing" - jumping on a moving train and riding a short distance - while other boys have been spoken to over the incidents.
Boys' High Board of Trustees' chairman Tim Robinson said the school did not tolerate the potentially dangerous behaviour.
It was working closely with KiwiRail to reinforce the safety messages to students. KiwiRail would be at the school's first two assemblies next term to tell students the potential consequences of such behaviour, he said.
"We are concerned for the safety and well-being of anybody who is taking part in this behaviour.
"We are also talking to Whangarei Girls' High to ensure we have got a consistent approach to dealing with anybody on the train tracks.
"We're also working with police to reinforce the rail safety message," he said.
"We're not happy with this behaviour and we are not prepared to accept it."
KiwiRail communities liaison manager Gill Evans said KiwiRail and TrackSAFE were working with schools in the area to ensure students were aware of safe behaviour around the rail corridor.
"Safety is KiwiRail's top priority and we are working with the local police and KiwiRail teams to make sure every incident that we see or hear about is reported," Ms Evans said.
"It can take a fully laden train up to one kilometre to stop, and usually the best that train drivers can do when they see something or someone on the tracks is to apply the emergency brakes and hope that they can stop in time."
Trespassing on rail tracks can attract a fine of up to $10,000.