She likes to be called Mrs White because that's what her darling kindergarten kids have called her for nearly 40 years. That's how long she's been teaching in the public system. And every year, she asks her students to write a letter.

Sometimes it's about what they want to do when they grow up. Sometimes it's something else, a memory, a feeling, an idea, those awkward kindergarten scrawls which pass for the alphabet, the green trees like lollipops, the sun with neat yellow rays.

And then she takes those letters and delivers them to the future.

That's what Tom Newby, 17, found in his letterbox this week, in that kindy handwriting, the memory that he wanted to be a detective when he grew up so he could find lost things and return them to their owners. He drew himself as an adult, smart red shoes, sun shining. Along with the drawing was a note from Mrs White.

Tom was one of 26 kids in the 2004 kindergarten class of Birchgrove Public School, Sydney, when Mrs White taught him; and the letter he wrote then has been keeping company with all the other hopes and dreams in a manilla folder in a filing cabinet.

Now they are being liberated through a process of Lynden White's detective work. Some students didn't move from their address 13 years ago. Some moved around the neighbourhood. One moved to the Central Coast in the middle of that kindy year. She remembers that little boy very vividly.

"I just Googled his name and there he was in the school newsletter," she says. His face looked unchanged from the little boy she'd taught so she posted his letter to his school on the NSW Central Coast. Some, trickily, appear to have only moved to Facebook and Mrs White thinks about that.

"How would they feel about having their old kindergarten teacher friend them?" she wonders.

Still, she's delivered nearly all of that year's letters to their owners - 21 of 26 - just as they begin the new stage of their lives, the end of school, the HSC and a world beyond the school gate. Some years, her strike rate isn't as good.

"They go missing and you never know where they end up but even if you get to 50 per cent, that's good."

So why does she pick this time of year?

"I want them to be content with whatever happens ... the HSC is not going to be the be all and end all. And I want them to be happy. There is more to life than those exams," she says.

She knows that some of her former students will be disappointed in their results – but she wants them to look beyond, to think about how far they have come since those early days of school.

"In kindergarten, you are learning a lot about yourself. [Teachers] concentrate a lot on social skills and laying foundations for later in life."

That's not to say that academic achievement is unimportant but it's different for different students.

"I have high expectations for kids and there is also all the curriculum expectations but I have always wanted kids to have fun, cooperating, collaborating, learning about themselves.

"To be in a classroom where we can make a mistake and it is not a problem, without being pressured. Just give them time, don't be in a hurry and once they are ready, they will fly. 

"I want them to remember how far they have come, where they have come from, and recapture some of that innocence."

When Ned Taranto, 18, Birchgrove kindy class of 2004, opened his letter last Sunday, he was reminded just how good Mrs White's memory was. When he was in kindy, the tuckshop had run out of tomato sauce for meat pies. At the time, the feisty five year old said it was an outrage! And Mrs White's note to him this week said that the speed with which 12 years had passed was an "outrage".

"She had a great memory," he remembers. His own letter reminded him of his unusual aspirations.

"I drew some weird gangster guy," says Ned. At five, he wrote: "I want to be a bling-bling because they are cool."

Ned now jokes: "Things haven't changed, I still like the jewellery and the gangster life."

With Tom's letter was also a note from Mrs White.

"Dear Tom," she begins. "I wonder if your career choice has changed. I ... want to wish you all the best and hope you achieve what you want."

At least one parent whose child received one of these letters told her: "You had us all in tears around the breakfast table."

Tom had no tears. He remembers Mrs White as a brilliant teacher who found exactly the right books for him to read and who saw him in the playground when he was in third class and they spent all lunchtime talking about painting.

"She was still keeping an eye on us all those years later," Tom remembers.

And the letter?

"It was very weird coming across something from myself that long ago. Also, the fact that she cared about me was really stunning. And god, I was adorable." He's laughing.

Turns out he was also adorable in kindy, an inquisitive kid, filled with life, really interested in the physical world, says Mrs White.

He still wants to be a detective.

Nope, not really. He wants to be an engineer which turns out to have more or less the same skill set.

"I have always enjoyed problem solving -  what is wrong with this situation and what can I do to fix it?"

Tom finishes his HSC in two weeks with the chemistry exam.