Seven Hills High School students will tackle the 14-kilometre run in this year's City2Surf race.
The 15 year 9 students will run in the August 10 event to raise funds for The Children's Hospital at Westmead after their peer, who has Crohn's disease, spent time at the hospital earlier this year.
Year 9 student Gerardo Sidari said the group began to train for the event by running laps of the school oval 11 weeks ago.
They now run the 9 kilometres from the school gates to Norwest Private Hospital, Bella Vista, after classes and several laps of the 3.2 kilometre circuit at Parramatta Park on a Saturday morning.
It is the first time each of the students in the group have entered the City2Surf.
Gerardo said the team members supported each other during training.
"Were ambitious about doing the run.
"Your registration fee goes to a charity of your choice so it's good that we can help out in that way."
The team will run in bright red shirts emblazoned with "Pain will pass, pride will last", a quote they found online.
"Running can be pretty painful but the pride we'll feel when we've finished will be worth it," Daide Chaker, 15, said.