Her room -- No. 3 -- is where she learned when she was in first grade.
"That room has good vibes," she said.
Harn started teaching in the room right out of college, and after this school year she'll retire. She said that when she began teaching first grade at Rollins it was pure luck that she was assigned to her original first-grade classroom, where she was taught by Margie Holland.
In her first year as a teacher, Harn and her mother were fixing up the classroom when her mom realized the unique connection.
"She said, 'Tina, I think this is your first-grade classroom.' We went back and looked it up (on a first-grade report card), and sure enough it was," Harn said.
Classroom No. 3 has had just a few changes through the years -- new desks, a lowered ceiling, a new sink and an erasable white board that replaced the old chalkboard.
Today, the classroom is filled with bright banners and posters, including one that challenges students to "Reach for the stars."
"The thing about that classroom is it's so big," Harn said Tuesday after teaching about synonyms and antonyms. "I just love my classroom."
And in her 29 years she has always taught first grade there.
"You see more progress in first grade than any other grade level," she said.
On Tuesday, one of her pupils, Jalen Simmons, said he will miss Harn when she retires "because she was the best teacher."
Besides her classroom, Harn will leave behind another connection to her past at Rollins. A good friend -- Mollie Silver, who met Harn when they were both 8 and attending Rollins -- is now a kindergarten teacher at the school.
"She is part of the reason I became a teacher," Silver said.
Harn said that these days she's teaching the children of pupils from years past.
She said that through the years her motto has been to instill self-esteem in her pupils.
"I think that's my legacy," she said. "I'm going to miss coming in every day and seeing their smiling faces."
She hopes whoever takes over No. 3 will let her come back to visit from time to time.
"I'm real picky about who's going to go in there," she said with a laugh.