As a journalist, it is not often you get to see a tangible example of the effect your work can have.
Sometimes you hope that a particular story will achieve something — expose an injustice or bring about much-needed change, but most of the time, the world goes on as it was.
So getting an invitation to return to Tanzania's School of St Jude — the subject of an Australian Story program I produced in 2005 — turns out to be a once-in-a-lifetime opportunity.
I am here because about 4,000 Australian families signed up to sponsor children at the school after watching the program and I have been invited as a special guest to witness the graduation ceremony of the first batch of students to complete high school.
It is a strange and humbling experience to be welcomed back as if I am the Bob Geldof of the School of St Jude.
"What's it like to see the school you built, Ben?" asks Gemma Sisia, who founded the school after moving from her home on a farm near Armidale, NSW, to Africa at the age of 22.
Since I was last here, the school has grown from housing 500 students to nearly 2,000.
"Those sponsors who signed up after watching Australian Story are the backbone of the school," she says.
"Time and again, I have said that St Jude's would not be the success it is today without the efforts of Australian Story."
Actor Rebel Wilson quietly signed up after seeing the program — several years passed before a young staffer in the St Jude's office recognised the sponsor's name as a star of film and television in Hollywood.
In the days leading up to the graduation ceremony, I keep meeting more and more sponsors who can trace their involvement back to the Australian Story broadcast.
About 70 sponsors have made the trip from Australia to be part of the ceremony, which will be the biggest celebration in the school's history.
I join one of them on a visit to the home of the student she sponsors.
Elizabeth Lekind, 20, lives with her older sister Naomi, Naomi's two young children and their two cows in a small cement house not far from the school.
Elizabeth has pledged to become a doctor, after a dramatic episode while doing volunteer work in a local hospital.
She encountered a woman lying in agony but receiving no attention from the doctors and no medicine.
She raised some money from friends and neighbours and came back the next day with the medicine — but the bed was empty.
"They said she had passed away that night. So I came home crying and that was the day I decided to want to be a doctor," she says.
"I want to help people. From that day, I pursued medicine."
Elizabeth Lekind believes Gemma Sisia has already transformed the future for her.
Without the School of St Jude, she would almost certainly be "married off" by now with several children, because her family could not afford higher education.
"I see her as a mirror to my future. Gemma came with a dream of providing free quality education to poor children, and she dreamt of bringing up the future leaders of Tanzania," she says.
"Many people would say that Gemma is a saviour. A saint."
On a second home visit, I meet eight-year old Emmanuel Kiwale in what can only be described as the slum of Arusha.
His family of five live in a tiny one-room wooden shack with no toilet.
Emmanuel is one of 104 St Jude's students who currently have no sponsor — another 165 are only part-sponsored.
His mother Mariam Omari says she is praying that God will send someone, a sponsor for her son, so that he can continue to study all the way to university and get a good job.
That would improve all of their lives.
As graduation day dawns, Gemma takes to the stage, her voice cracking with emotion.
"It seems like only yesterday that you enrolled. I remember when we were issuing your uniforms," she says, to thunderous applause.
"I remember when you got sick. I remember when you sat your first national exams. You are the reason for this very special day."
As celebrations wind up with the presentation of the giant graduation cake — a cake that turns out to be a decorated, barbecued goat — I feel my faith in humanity being restored.
To be a part of this project where so many people have worked together for a worthwhile goal has been an uplifting experience.
As I say to the students when it is my time to speak, it will be fascinating to watch their progress over the next 20 or 30 years.
What if the future Tanzanian president, groundbreaking scientist or world famous musician is in this room today?
And so now, if my children or future grandchildren ever ask whether I have done anything to make the world a better place, I have a ready answer.
It is my small part in the success of the School of St Jude.
In Tanzania, where a cornfield once lay, now stands a school.
Where kids formerly had no better prospects than minding cows, 2,000 children are getting a great education.