Rarely do teachers know whether they make lasting impressions on students — and finding out they did can be one of the most profound rewards of all. I know because it happened to my mother, a retired teacher, when she turned on NPR one morning in 2003.

The story began long before that, in the mid-1960s. My parents had been living for a few years in Burlingame, a suburb of San Francisco, where they’d driven days after marrying in small-town Iowa in 1963.

My dad worked as a junior lawyer at a firm in the city. My mom stayed closer to home, teaching English at Burlingame Junior High. I know little else about their lives at the time but for a few details I foggily recall them mentioning — the drinking at office parties that struck my dad as recklessly heavy; the precocious redhead, Tamara, who loved writing stories as a seventh-grader in my mom’s class.

My parents moved in 1967 to Chicago, then settled a year later in Oregon, where my mom stayed home for several years to raise my two older brothers and me. She went back to the classroom when I was in elementary school, and she taught on and off until she was in her 60s.

I was visiting them in 2003 when my mom came out of my parents’ room with a puzzled look on her face. She’d been listening to the radio, and she had heard an interview with a best-selling author of young adult fantasy novels. The woman’s name was Tamara Pierce — the same as the redhead my mom had taught nearly four decades before. My mother wondered: Could it be the same person?

Well, I said — probably far too snarkily — the Internet should be able to tell us. I logged on to the desktop in my dad’s cluttered basement office and quickly found the website for the author, whose name I’d misspelled when searching. It was Tamora, not Tamara, and she was a big deal — an “enormously popular” writer, as a New York Times review put it that same year, of books featuring powerful female heroines.

I clicked on the biography link to scan for references to Burlingame, and my heart began to flutter when I spotted it at the bottom of the first section — here was confirmation that my mother had taught a now-famous writer! But my eyes came to a standstill reading the next paragraph, in which Pierce described writing her first fiction as a sixth-grader.

“The next year, as I was still scribbling my own stories, my English teacher (bless you, Mrs. Jacobsen!) introduced me to The Lord of the Rings trilogy by J.R.R. Tolkien,” the biography read. “I got hooked on fantasy, and then on science fiction, and both made their way into my stories.”

My mother’s name was Mary Jacobson.

I don’t remember my mother’s immediate response to this discovery, but I’d guess it was muted and might have brought a deeper blush to her naturally rosy cheeks. My mom, who died in 2011, was kind, quietly intelligent and a dear friend and confidant to more people than I’ve ever counted as companions. But she was also extremely humble.

Within days, my dad had checked out all the Tamora Pierce books at the local library, and in one we found another Easter egg: “Daja’s Book,” a 1998 novel, was dedicated to “the teachers who shaped my life.” Pierce listed four names, and one was Mary Jacobsen. (This misspelling of our family name was no surprise. It happened all the time.)

The dedication concluded: “A great teacher is above all treasures.”

I cherish this story not only because it’s a wonderful demonstration of the impact teachers can have without knowing it. It also made me see my mom differently. She was just 24 when she taught Pierce — and she introduced her to Tolkien?

I was a voracious reader as a child and teen, and I attribute that to the hours my mom and I spent reading on my bed together — first Beatrix Potter’s “Appley Dapply’s Nursery Rhymes,” later Jean Craighead George’s “Julie of the Wolves.” But I don’t remember her ever mentioning Tolkien.

Maybe my mom was simply astute enough to recognize that fantasy wasn’t my bag. I never did read Tolkien, and I couldn’t get past 20 minutes of the “Lord of the Rings” film. (I do, however, watch “Game of Thrones,” so I guess we all can evolve.) And maybe she was perceptive enough to know Tolkien was what Pierce needed.

In a recent email, Pierce, who goes by Tammy, remembered clearly that my mom gave her the first book of the trilogy on a Friday and the second two on the following Monday. “She changed my life,” Tammy wrote. Tolkien inspired her to write not only what she called “high fantasy,” she said, but also to write female-centric books with kid heroes.

Tammy shared other specific memories. My mom was “the first adult I’d known who came across as a human being,” she said, recounting Mrs. Jacobson’s wry smile when, one day after telling her students that they’d need notes from their parents to read the then-controversial “The Catcher in the Rye,” every kid showed up with one.

When young Tammy wrote a too-long short story about Blackbeard, my mom suggested that she pick shorter subjects for assignments but to press on with bigger projects in her spare time. My mom also told her to keep everything she wrote — advice that Tammy, now the author of 31 books and numerous short stories and essays, said she still heeds.

My mom emailed Tammy after we found her website in 2003, and the writer says she remembers they both said they’d thought of the other often.

“I was so grateful to be able to tell her at last what she had done for me, because I think my life would have been very different without the books she introduced me to, the critiques she gave my writing, and the way she made it clear that she thought I was someone special,” Tammy told me. “I was very short on these things in those years, and without her saying so, she gave me belief in myself.”

In June 2011, when I was living overseas as The Post’s correspondent in Islamabad, Pakistan, I came home to Oregon for a few weeks. My mother had been battling ovarian cancer for five years, and various cocktails of chemotherapy had become unable to stop its march. Weakened and mostly confined to bed, she smilingly received a steady stream of friends. She was dying, and she was saying goodbye.

As part of this wrenching process, she asked me to email Tammy, which she was too weak to do herself. Here is part of what I wrote:

I was helping her clean and organize her closet and dresser drawers, and she said it reminded her of how you, as a student, would stay after school to straighten her desk. ‘She was so cute at doing that. She was so concerned at the end of the day,’ my mom said of you. ‘Tell her how much I appreciated it.’ She also recalled that you were the ‘primary instigator’ and director of a class play, ‘Iphigenia.’ She had no idea how to direct, she said, and was so grateful that you took on that role.” 

Tammy immediately sent a heartfelt card to my mom.

This is Teacher Appreciation Week, and as I prepared cards and gifts for my children’s teachers, I thought about this story. It made me consider how nice it would be if we all let our favorite former teachers know their work mattered. (I’m certainly guilty of not having done so. Thank you to my high school English teacher, Mr. Bumstead!)

My mother was humble, but that end-of-life request — that I wish Tammy well — also showed me she was proud. Proud, surprised and so very delighted to know that she’d made a difference.

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