Horizons Regional Council Roadsafe co-ordinator Glenda Leitao said they had to be careful with their mock crash scenes when the decision was made to include a fatality.
"She will actually be taken away in a body bag," Ms Leitao said of Charlotte. "She was all for it."
It was up to the school to decide whether or not they were comfortable with including a death in the scenario, and for some it might be "too close".
"We have to be always very aware as to what's happened in the particular school," Ms Leitao said.
If there were any deaths recently to affect the students, they had to take this into consideration.
Monday's demonstration was organised by three students, members of SADD which previously stood for Students Against Driving Drunk, but now means Students Against Destructive Decisions.
The scenario involved two teenage boys in one car crashing into a car of three girls after the driver became distracted.
"It's not about alcohol," Ms Leitao said.
"The driver's been distracted by somebody which has caused a crash."
The message was that the driver needed to concentrate on driving.
Wanganui Fire Service fire risk management officer Shane Dudley spoke to students on a microphone, explaining that police had the power to seize the driver's phone following the accident to see if he'd been using it while driving.
Maggie Symes, 17, thought the mock crash was "really good" and showed what a crash was like in real life.
"No one's really seen crashes that often," she said.
Mr Dudley said the exercise was "fantastic" and everyone got a lot out of it.
Some students were roped in to help out emergency workers.
"By the time we turned up, people were more than happy to come and help out.
"I guess people just need a little bit of direction. Once you get someone with a little bit of authority, people are more than happy to get stuck in."
When firefighters were out on a fire call they never had any trouble getting people to help them, he said.
He wanted to stress the message not to be distracted while driving.
"It might be so easy to keep on texting ... but you don't have to be going fast to really, seriously hurt someone. It's not unheard of that we have to cut somebody out of a car in the middle of town."
The scene was attended by fire, police and St John paramedics, as well as Cleveland Funeral Services.